Start Here: Identify Your Symptom
“My PC won’t boot” actually covers about a dozen distinct problems. Before you do anything else, figure out which of these you have:
- No power at all — no fans, no lights, nothing happens when you press the power button.
- Power but no display — fans spin, lights come on, but the monitor stays black.
- POSTs but won’t reach Windows — you see the manufacturer logo, maybe BIOS, then it hangs or restarts.
- BSOD or restart loop — Windows starts loading but crashes or reboots repeatedly.
- Beep codes or error LEDs — diagnostic beeps or motherboard LEDs are reporting an error.
Each scenario has a different troubleshooting path. Skip to the section that matches your symptom.
Scenario 1: No Power at All
If your PC shows zero signs of life when you press power, work through these in order:
Check the wall outlet. Plug a lamp or phone charger in to confirm power. It sounds dumb until it’s the answer.
Check the PSU switch. On the back of your power supply, there’s a physical I/O switch. It should be on “I”. This gets bumped surprisingly often.
Check the front panel header. Open the case and confirm the power switch cable from the front of the case is properly seated on the motherboard’s “PWR_SW” header. If you’ve recently moved your PC, this can come loose.
Test with a paperclip. Unplug all motherboard connections from the PSU. Bridge the green wire and any black wire on the 24-pin connector with a paperclip while the PSU is on. If the PSU fan spins, the PSU works. If not, replace the PSU.
Scenario 2: Power But No Display
This is the most common failure mode and usually indicates a memory, GPU, or motherboard problem.
Reseat the RAM. Remove all RAM modules, then put one back in slot A2 (the second slot from the CPU on most boards). If it boots, add the others one at a time.
Reseat the GPU. Pull the graphics card and reseat it firmly. Confirm the PCIe power connectors are fully plugged in.
Try integrated graphics. If your CPU has an iGPU, remove the GPU entirely and plug the monitor into the motherboard. If you get display, the GPU is the problem.
Check the monitor cable. Try a different HDMI/DisplayPort cable and a different port.
Clear CMOS. Remove the motherboard battery for 30 seconds, then reinsert. This resets BIOS to defaults.
Scenario 3: POSTs But Won’t Reach Windows
If you see the BIOS splash but Windows won’t load:
Enter BIOS and check boot order. Make sure your Windows drive is set as the first boot device.
Try Windows Recovery. Boot from a Windows installation USB → Repair → Troubleshoot → Startup Repair.
Check disk health. From Recovery → Command Prompt: chkdsk C: /f /r
Disable Fast Startup and Secure Boot temporarily in BIOS to rule out incompatibility.
Scenario 4: BSOD or Restart Loop
If Windows starts loading then crashes:
Boot to Safe Mode. If Safe Mode works, the problem is a driver or software issue. Uninstall recent updates, drivers, or programs.
Check the BSOD error code. WHEA_UNCORRECTABLE_ERROR usually means CPU or RAM; MEMORY_MANAGEMENT means RAM; CRITICAL_PROCESS_DIED often means corrupted system files (run sfc /scannow).
Run Windows Memory Diagnostic. Type “Memory” in Start menu → Restart and check.
Stress test the CPU. Use Prime95 for 30 minutes; if it crashes, you have a CPU or VRM problem.
Scenario 5: Beep Codes or LED Errors
Most modern motherboards have either Q-LEDs (4 small LEDs labeled CPU, DRAM, VGA, BOOT) or beep speakers. The LED that stays lit indicates which subsystem is failing:
CPU LED stays on: CPU not detected — check CPU power cable, reseat CPU, check for bent pins.
DRAM LED stays on: RAM issue — reseat, try one stick, try different slots.
VGA LED stays on: GPU issue — reseat, try different GPU or use iGPU.
BOOT LED stays on: No bootable device found — check SATA/NVMe connections and boot order.
When to Give Up and Get Help
If you’ve worked through all the relevant scenarios and your PC still won’t boot, you’re likely looking at a dead motherboard, CPU, or power supply. These can be expensive to diagnose without proper testing equipment. Most cities have computer repair shops that will diagnose for $50-100 and tell you what’s wrong before you commit to repair.