PC keeps restarting or cannot boot: a diagnostic sequence
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When a new PC keeps restarting, I’d return to a simple default setup and work through one change at a time. The point at which it restarts gives you a useful starting clue: before the BIOS, during Windows startup or under load.
Note whether you see the BIOS logo, can enter firmware settings, reach the Windows loader or only fail during a game. Record diagnostic lights and the most recent hardware or settings change.
Memory training may include restarts. Follow the board’s documented expected behaviour before calling the process a boot loop.
When a component replacement is justified, choose a compatible motherboard or matched RAM kit. Keep the stable-default first-boot sequence in the beginner guide.
For restarts before the operating system
Check CPU support and firmware, memory seating and the recommended slot arrangement. Return to documented default settings before diagnosing an EXPO/XMP configuration.
Disconnect power before reseating parts. Test one module in the recommended position and compare modules in the same slot. Keep a record instead of changing several variables together.
For a machine that reaches BIOS but not Windows
Check whether the intended system drive is detected and the boot selection is correct. A newly installed blank SSD is not an operating system.
Check installation-media and disk-selection details without formatting anything speculatively. Back up important files before reinstalling, repairing partitions or replacing storage.
For failures under load
Check temperatures, fan operation, power connections and the relevant driver or application error. Remove optional tuning and repeat the same workload at a stable baseline.
A sudden restart is not proof that the PSU is defective. CPU, memory, software and other faults can produce similar symptoms. Use evidence or known-good substitution to narrow the cause.
Choose the next check
Use memory diagnosis for profile or capacity problems and temperature checks if sustained load precedes the failure.
If a supported default configuration still fails and safe simple checks are exhausted, use manufacturer support or a repair service rather than buying a series of speculative replacements.