PC Won't Boot: Complete Troubleshooting

Ninety percent of no-boot issues have four root causes: RAM not seated correctly accounts for 40% of cases, loose power cables cause 30% of failures, incorrect BIOS settings create 15% of problems, and a dead PSU is responsible for the remaining 5%. The paper clip PSU test, reseating RAM in different slots, and clearing CMOS resolve the vast majority of issues without any parts replacement.

Systematic Troubleshooting Steps

1. Check all power connections — reseat the 24-pin ATX and 8-pin EPS CPU connectors

2. Remove and reseat RAM, test with a single stick in slot A2 first

3. Try clearing CMOS by removing the motherboard battery for 30 seconds

4. Perform the PSU paper clip test to confirm the power supply is working

5. Check for bent CPU socket pins (Intel) or damaged AMD AM5 pins

6. Boot with minimal components — CPU, one RAM stick, no GPU (use integrated graphics)

7. Listen for POST beep codes and check your motherboard's debug LED indicators

Common Error Codes

Modern motherboards include a 2-digit debug display. Common codes: A0 means IDE init, 00 usually means boot success, and any code in the 90s typically indicates a CPU or RAM initialisation problem. Consult your motherboard manual for a full list.