Why won't my pc boot?
Quick Answer
Your PC won't boot likely due to a power supply issue, loose RAM sticks, a failing graphics card, or a corrupted operating system on your primary drive, preventing the system from completing its Power-On Self-Test or loading Windows 10/11.
Understanding PC Boot Failures
When your PC refuses to boot, it typically falls into one of three main categories: no power at all, a Power-On Self-Test (POST) failure, or an operating system (OS) loading failure. A 'no power' scenario means the computer is completely dead, with no fans spinning, no lights illuminating, and no sound. This often points to problems with the wall outlet, the power cable, or the power supply unit (PSU) itself, like a dead Corsair RM750x.
POST failure occurs when the computer receives power but cannot successfully initialize essential hardware components such as the CPU, RAM, or graphics card. You might see diagnostic lights on your motherboard (like ASUS Q-LEDs for CPU, DRAM, VGA, BOOT) stay lit, or hear a series of specific beeps (e.g., one long, two short beeps often indicates a video card issue on an AMI BIOS system). This stage happens before any operating system can even begin to load.
An OS loading failure means the hardware passes POST, but the computer struggles to find or load the operating system from your storage device, such as an NVMe SSD like a Samsung 970 EVO Plus or a traditional HDD. You might see messages like 'No Boot Device Found,' 'Operating System Not Found,' or a spinning circle with no progress. This indicates issues with the boot order in BIOS, a corrupted Windows 10 installation, or a failing storage drive.
How to Diagnose and Fix a Non-Booting PC
First, you need to check the power source. Ensure the power cable is securely plugged into both the wall outlet and the PC's power supply unit, verifying the PSU's physical switch is flipped to the 'I' position, not 'O'. If the PC is still completely dead, try a different power cable or plug the PC into a different wall outlet that you know works, bypassing any power strips or surge protectors temporarily. If you have a modular PSU, confirm all cables, especially the 24-pin ATX and 8-pin CPU power, are fully seated.
Next, listen for any beep codes or look for diagnostic LEDs on your motherboard. Many modern motherboards, such as a Gigabyte Aorus Z690 or an MSI B550, have four small LEDs labeled CPU, DRAM, VGA, and BOOT. If one of these stays illuminated, it pinpoints the failing component. For example, if the DRAM LED remains lit, proceed to reseat your RAM. Power down the PC, unplug it, open the side panel, unclip the RAM sticks (like a G.Skill Ripjaws V DDR4-3200), remove them, and firmly reinsert them into their slots until the clips snap into place. Try booting with just one stick of RAM in the recommended primary slot (often DIMM_A2) for 30 seconds to test each module individually.
If reseating RAM doesn't work, try reseating your graphics card. Unplug the PCIe power cables, unclip the GPU (like an NVIDIA GeForce RTX 3070) from its slot, pull it out, and then reinsert it firmly, ensuring the locking mechanism engages. Reconnect the PCIe power cables. If you have integrated graphics, remove the dedicated GPU and try booting using the motherboard's video output. Additionally, clear your CMOS (Complementary Metal-Oxide-Semiconductor) settings. To do this, unplug the PC, locate the small CR2032 battery on the motherboard, remove it carefully for at least 30 seconds, and then reinsert it. Alternatively, find the 'CMOS Clear' jumper pins on your motherboard (refer to your manual) and temporarily short them with a screwdriver for 10-15 seconds.
Finally, if the PC powers on but displays a message like 'No Boot Device Found,' access your BIOS/UEFI settings by pressing F2, Del, or F10 repeatedly during startup. Navigate to the Boot tab or Boot Order section and ensure your primary storage drive (e.g., your Western Digital Black SN750 NVMe SSD) is listed first in the boot priority. If the drive isn't listed, check its SATA data and power cables, or M.2 slot connection. If the boot order is correct and the drive is recognized but Windows 10 still won't load, you may need to repair or reinstall your operating system using a bootable USB drive, which typically takes 20-45 minutes for a fresh installation.
Common Mistakes to Avoid
One frequent error is overlooking the most basic power checks. Many people immediately assume a complex hardware failure when the issue is simply the power supply switch on the back of the PC being in the 'O' (off) position, or the power cable not being fully inserted into the wall outlet. Always confirm the power source, the cable, and the PSU switch are correctly configured before attempting any internal diagnostics.
Another common mistake is failing to check all internal cable connections thoroughly. Users might reseat RAM but forget to check the 24-pin ATX power cable to the motherboard, or the 8-pin CPU power cable near the CPU socket, especially after opening the case for cleaning or upgrades. A loose connection, even if it looks plugged in, can prevent the entire system from powering on or passing POST, leading to frustrating troubleshooting sessions.
Many individuals panic and jump straight to reinstalling the operating system without performing basic hardware diagnostics first. If the PC isn't even reaching the stage where it tries to load Windows 10, reinstalling the OS is a wasted effort and won't resolve a hardware problem like a faulty RAM stick or a dead graphics card. Always confirm the hardware is functioning correctly before addressing software issues.
Ignoring motherboard diagnostic indicators or beep codes is also a significant oversight. Modern motherboards provide valuable clues through their debug LEDs (e.g., CPU, DRAM, VGA, BOOT) or by emitting specific beep patterns. Consulting your motherboard's manual for these codes can quickly narrow down the problem to a specific component, saving hours of guesswork and unnecessary component swapping.
Expert Tips for Best Results
Always keep a bootable USB drive with your operating system's installation media (like a Windows 10/11 installer) readily available. This allows you to quickly attempt repairs, access recovery environments, or perform a clean installation if the issue is software-related or if your primary drive needs formatting. Having this prepared saves significant time when a boot failure occurs.
When troubleshooting, document every step you take and any observable symptoms. Write down specific error messages, the exact beep codes you hear, which diagnostic LEDs are lit, and what components you've reseated or swapped. This organized approach helps you track what you've tried, prevents repeating steps, and provides crucial information if you need to seek further assistance from a technician or online forums.
Invest in a quality multi-meter and learn basic power supply testing. While not always necessary, a multimeter allows you to check the voltage outputs of your PSU's various connectors (e.g., 12V, 5V, 3.3V) to confirm if it's delivering stable power. A faulty power supply can manifest as intermittent boots, sudden shutdowns, or a completely dead PC, and testing it can quickly rule it in or out as the culprit.
Understand your motherboard's manual inside and out, especially the sections pertaining to POST codes, debug LEDs, and CMOS clearing procedures. Every motherboard model, such as an ASUS ROG Strix B660 or an ASRock Z790, might have slightly different indicators or specific jumper locations. Familiarity with your specific board's documentation will make diagnosing hardware issues much faster and more accurate.
Frequently Asked Questions
My PC turns on but shows no display, what's wrong?
This usually indicates a problem with your graphics card, monitor, or the display cable. First, ensure your HDMI or DisplayPort cable is securely connected at both the PC's GPU output and the monitor's input. Try a different cable or connect your PC to another known-working monitor or TV. If you have a dedicated graphics card, remove it and try connecting your display to the motherboard's integrated graphics output, if available, to rule out the GPU as the cause.
My PC makes a clicking noise and won't boot, what does that mean?
A clicking noise often points to a failing traditional hard drive (HDD) or, less commonly, a struggling power supply unit. If the clicking is rhythmic and comes from the storage area, it's highly likely your HDD is failing and preventing the system from booting. If the sound is more like a faint electrical click from the PSU area, the power supply might be struggling to deliver adequate power, especially under load, and needs to be tested or replaced.
How do I clear CMOS on an MSI motherboard?
To clear CMOS on most MSI motherboards, first power down and unplug your PC. Then, locate the two 'JBAT1' pins on your motherboard, usually near the battery. Use a small metal object, like a screwdriver, to short these two pins together for about 10-15 seconds. Alternatively, you can remove the small CR2032 battery from its socket for 30 seconds and then reinsert it. This resets your BIOS settings to their factory defaults.
What if my PC boots to BIOS but not Windows 10?
If your PC successfully enters BIOS/UEFI but fails to load Windows 10, the issue is typically with your boot order, the Windows installation itself, or a failing storage drive. Enter BIOS, navigate to the 'Boot' section, and ensure your primary Windows 10 drive (e.g., your Kingston KC3000 SSD) is set as the first boot option. If it is, try using a Windows 10 installation USB to perform a 'Startup Repair' or, as a last resort, a clean reinstall, which usually takes 20-45 minutes.
Can a faulty power supply prevent a PC from booting entirely?
Yes, absolutely. A faulty power supply unit (PSU) is a very common reason for a PC not to boot at all. If the PSU fails to deliver the necessary voltages (e.g., 12V, 5V, 3.3V) to the motherboard and components, the system will remain completely dead, with no fans spinning, no lights, and no signs of life. Testing the PSU with a dedicated tester or by swapping it with a known-good unit is crucial in this scenario.