PC restarting with a click sound

[tech_lover]

Hi,

My old PC is restarting by itself after 1-2 hours of operation after a click sound. How can I diagnose the problem? It is a 2.53GHz Sempron.

[NucleusKore]

Diagnose!!!!! Run and back up all your data. It may be a sign of an impending head crash.

[patkim]

I assume you have Windows. Use some tweaking utilities like ‘Customizer XP’ to ensure that option in registry “Automatically restart Windows when Explorer crashes” is disabled.
After this if the problem goes away… it most likely was a software (OS) problem.
Else one or the other hardware is malfunctioning could be right from SMPS to Motherboard. As you have indicated it’s an old PC, most likely some hardware is on verge of giving up.