PC Troubleshooting: What to Do When Your PC Won’t Start

If you’re having trouble getting your PC to turn on, don’t worry, you’re not alone. Dealing with a non-booting PC is a common issue that many computer users face. The good news is that there’s plenty of information available to help you troubleshoot and fix the problem. In fact, troubleshooting your computer yourself can be a rewarding and educational experience. So if you’re interested in learning how to solve PC boot issues, keep reading for some valuable tips.

Common Reasons Your PC Won’t Start

PC power supply cables on a modular PSU.
*Image used with permission by OnSpec Electronic, Inc.*

When your PC refuses to turn on, it can be frustrating. However, the fact that nothing happens when you press the power button can be a clue in itself. Somewhere between pressing the power button and power being delivered to the components, there’s likely a problem. One of the most common culprits is incorrect connections.

So, let’s start with the basics. Is the power cable plugged into the wall socket and your power supply? Are both the wall socket and PSU switched on? Double-check these connections to ensure everything is properly connected. Additionally, make sure the motherboard and CPU power cables are correctly plugged in. For more detailed information on this, refer to our comprehensive PC build guide.

If you’re still getting absolutely no response when you press the power button, check if your motherboard has any idle indicator lights. These lights can confirm whether or not the motherboard is receiving power. Before assuming you need a new power supply, try swapping out the power cable and using a different wall socket. If you do end up needing a new power supply, check out the best ones available on the market.

If your motherboard does receive power but your PC still won’t start, the next step is to check the connection of your front-panel button. Each computer case is different, but most have a series of cables running from the front panel to a point on the motherboard, usually found at the bottom-right. To inspect the connection, remove your case’s side panel and locate the cable. Ensure that it is properly connected to the motherboard. The pin layout may vary, but it generally resembles a two-wide row of pins enclosed in a plastic box.

The cables themselves are labeled, such as “HDD LED” or “PWR.” Some cables also have positive and negative contacts. Make sure they are securely seated on the corresponding pins, which are either marked next to the pins on the motherboard or detailed in the motherboard’s documentation. When in doubt, unplug and reconnect them.

No Display or Boot Failure

If your PC powers on, fans spin, and lights turn on, but nothing appears on the screen, it could indicate a hardware issue. Before diving into the system, it’s important to protect yourself from static buildup. Work on a flat, non-conductive surface like a wooden or plastic desk. If you’re on carpet, consider wearing shoes. Also, periodically touch the case to ground yourself.

Check the Monitor

The first step may seem obvious, but it’s often overlooked. Ensure that your monitor is plugged in and connected to your PC using the correct cable. Check the indicator lights on the monitor to confirm if it’s turning on. Additionally, make sure the monitor cable you’re using is functioning properly. In some cases, turning up the brightness levels can resolve display issues.

Diagnostic Codes and Beeps

Many modern motherboards can provide error codes or beeps that indicate the problem. Consult your motherboard’s manual to diagnose the issue based on these indicators. The error codes can range from simple errors, such as forgetting to plug in a power cable, to more severe issues, such as a damaged CPU. Refer to your documentation for guidance in translating the error code specific to your machine.

SATA cable plugged into motherboard.
*Image used with permission by OnSpec Electronic, Inc.*

Is Something Shorting?

If your PC powers on, but immediately shuts off and repeats the process in an endless loop, there may be a metallic object causing a short circuit within the system. A short circuit occurs when improper electrical connections are made between components. For example, a frayed wire might come in contact with the motherboard, or a part of the case may touch a component. Did you accidentally drop a screw behind the motherboard? Check that all wires are intact, ensure that no part of the case is directly touching the exposed PCB, and verify that the motherboard is installed on standoffs that elevate it from the case surface.

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Diagnosing a short circuit can be challenging, but if your system exhibits these symptoms, it’s worth considering the possibility. To prevent a short circuit, you can remove all components from the case and rebuild the system on a desk. However, this is an extreme measure. If you suspect an errant screw is causing the problem, tilting the case from side to side can help locate it.

Reset the CMOS

It’s possible that the issue isn’t hardware-related, but rather a compatibility problem or settings error in your system’s BIOS. The BIOS code runs before the operating system starts up and helps configure the PC for use. If this is causing the problem, there’s a relatively simple fix.

If your motherboard has a CMOS reset switch or button, use it according to the instructions provided in the manual. Otherwise, unplug the power cable from your PC and locate the flat, silver battery on the motherboard. Remove it, press and hold the power button on your PC for 30 seconds, then plug the battery and power cable back in and try again.

If your motherboard is older than your CPU, there may be a compatibility issue that prevents your PC from starting. In this case, consider fully updating the BIOS.

Note: If you had any custom BIOS settings, such as fan profiles, overclocking, or specific drive configurations, you’ll need to reconfigure those settings after resetting or updating the BIOS.

Reseat All Power Cables

Attaching the 24-pin power connector to a motherboard.
*Image used with permission by OnSpec Electronic, Inc.*

A PC has various power plugs, and it’s easy to overlook one when your PC won’t turn on. One crucial connection is the 4/8-pin connector(s) located near the CPU. Additionally, check the wide 24-pin connection. Many builders forget about the smaller CPU power connection. Even if they are properly plugged in, it’s a good idea to unplug and reconnect them to ensure they are functioning correctly.

Next, check all other components in the PC to ensure there’s power running from the power supply to each one. In a typical build, this includes hard drives, optical drives, and possibly a PCIe expansion card or graphics card. If you have a modular power supply, verify that all cables are correctly connected to the correct spot on the PSU and are connected to the appropriate component.

If all power connections seem secure, try starting the PC with only the essential components connected. If it works, gradually reconnect each component to identify any faulty ones. The minimum components required are:

  • Motherboard 24-pin and 4/8-pin power cables.
  • CPU cooler.
  • Graphics card (unless using the onboard GPU) and any required 6/8-pin power cables.
  • A single stick of memory.
  • Boot drive with power connector and data cable (if it’s a SATA drive).


A CPU AIO watercooler pre-installed.
*Image used with permission by OnSpec Electronic, Inc.*

Installing a CPU is relatively straightforward, but there’s always a chance that something went wrong, such as improper cooler installation or forgetting to lower the retention arm.

If you suspect an issue with the CPU when your PC won’t turn on, consider removing and reinstalling it. Intel CPUs only fit in one direction because of notches on one side of the chip that align with notches in the socket. If you installed the chip yourself, make sure you removed the protective black plastic piece that sits in the motherboard slot to cover the pins. The chip should be clamped down by a frame around the socket, and a small arm next to it should be securely tucked underneath the clip. It requires a firm amount of pressure to clamp the chip down.

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With AMD CPUs, look for a golden triangle on one corner of the chip and align it with the triangle on the socket. Once it’s fully seated into the socket, carefully lower the arm next to the socket to secure the chip in place.

Improper CPU installation can result in bent pins, a damaged cooler, or a compromised motherboard. Check the surrounding area for any damage, such as bent pins in the socket or CPU, before reinstalling the chip.

If you spot bent pins, they are likely the cause of your problem. Attempting to fix this issue yourself requires extensive research or, ideally, professional assistance.


RAM in motherboard slots.
*Image used with permission by OnSpec Electronic, Inc.*

Memory problems can cause a variety of PC issues. If you suspect your memory is the culprit, here’s how to investigate.

Before removing anything, ensure that the memory you installed is compatible with your system. Did you purchase the correct generation, such as DDR4 or DDR5?

RAM tabs on motherboard.
*Image used with permission by OnSpec Electronic, Inc.*

Assuming you have the correct memory, it must be installed in the proper slot or slots, facing the correct direction, and fully seated. Consult your motherboard documentation for the correct slot configuration. If you have a dual-channel kit with two identical memory sticks, there is usually an empty slot between them. However, the configuration varies between Intel and AMD systems. After determining the proper slots, align the notch on the bottom edge of the memory stick with the plastic riser in the slot. Firmly push down until the tabs on either side of the slot click inwards and secure the memory stick. If the notch is visible, the RAM is not fully installed. It’s a good idea to remove and reseat it, even if it appears to be properly seated.

It can also be helpful to boot with only one stick of RAM to test if the other one is defective. You can also try different slots to check for any damaged slots that may prevent successful booting.

Graphics Card

The easiest way to diagnose a graphics card problem is to try using a different one. If you have a spare graphics card, remove the original and replace it with the spare to see if the system boots. If it does, your original GPU may be the issue.

If you don’t have a spare graphics card, but your PC has onboard graphics, you can still test your GPU. Uninstall your graphics card and connect your display to the motherboard’s display output. If the system boots, there’s a possibility that your graphics card is causing the problem.

If you suspect the GPU is at fault, try reseating it anyway. Sometimes, simply reconnecting a component can resolve the issue.

Installing a graphics card into the PCIe slot.
*Image used with permission by OnSpec Electronic, Inc.*

Also, consider using different PSU cables for power if available and avoid using power adapters whenever possible. Additionally, try inserting the graphics card into a different PCIe slot on your motherboard if there is one.

If you have a separate GPU, ensure that your monitor is connected directly to the graphics card, not to the video port on your motherboard. If the monitor appears to be malfunctioning, try connecting a different display to see if that resolves the issue. For more complex setups with multiple monitors, refer to our guide on multi-monitor troubleshooting. However, it’s generally recommended to start with a single screen and add more once everything is functioning correctly.

CPU Cooler

CPU cooler inside the Asus ProArt PD5 desktop.
*Image used with permission by OnSpec Electronic, Inc.*

If your PC powers on for a short period before unexpectedly crashing, it could be a sign of a malfunctioning cooler. Sometimes coolers can be defective, but installation issues are also common. First, ensure that you can hear the cooler running. If it doesn’t sound like it’s running at all, verify that the fan is properly connected to the motherboard’s fan header. Most motherboards label the fan header for easy identification. However, more complex coolers might require multiple connections depending on the design.

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If the fan is running correctly and securely connected, the issue might lie with the thermal paste between the cooler and the CPU. Thermal paste is essential for transferring heat from the processor to the cooler. If applied incorrectly or if you’re using the wrong type of paste, the cooler won’t effectively dissipate heat. If you suspect this is the problem, it’s best to reseat the cooler as soon as possible to prevent your processor from overheating again.

Detach the cooler, remove any dried thermal paste that may be in the way (99% isopropyl alcohol is useful for cleaning), and reseat the cooler with a fresh dot of thermal paste in the center. Carefully place the cooler on top of the processor and partially tighten any brackets or screws in a sequential manner to avoid putting excessive pressure on any specific part of the processor. Remember, you only need a small amount of thermal paste, and it should not squeeze out or run off the sides during installation.

The System Begins to Boot, but Fails

If your PC powers on, displays a signal on the screen, but fails to reach the operating system before shutting down, the list of potential problems is relatively short.

First, check the physical connections of the hard drive. If you’re using an NVMe SSD, ensure it’s properly plugged into the M.2 slot. As with other components, if it appears to be improperly seated, remove and reinstall it.

For SATA SSDs or hard drives, two connections are required: one for power and one for data. The power cable should run from the power supply to the drive, and there may be other similar connections on the same cable for multiple drives. The data connection should link the drive to the motherboard. Verify that both ends of the connections are securely plugged in.

Attaching front panel USB connectors to a motherboard.
*Image used with permission by OnSpec Electronic, Inc.*

If your motherboard has additional settings options, such as RAM optimization modes for gaming, ensure they are turned off for troubleshooting purposes. Avoid any overclocking that may cause your PC to shut down before it can properly start. Once you have the system running smoothly, you can explore overclocking strategies if desired.

Often, resetting the CMOS is all that’s needed to resolve booting and posting issues. If your motherboard has a reset button, press it following the manufacturer’s instructions. If it doesn’t have a reset button, you’ll need to remove the battery.

If the OS logo remains on the screen while the PC is rebooting, there may be an installation issue. You can attempt to boot into safe mode to rectify the problem. If you recently switched to Windows 11, the new operating system might place greater demands on your hardware, potentially causing boot failures on older systems. Ensure that your PC meets the system requirements for Windows 11, or consider reverting to Windows 10 if necessary.

If all else fails, refer to our helpful guide on how to restore Windows to its original settings.

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OnSpec Electronic, Inc.

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