So I'm back.
My dad's desktop computer went blank last night. The entire tower just died. The peripherals work just fine - power lights on - but no lights on the tower.
Power supply is firmly attached and on.
Nothing's been done in the case since I replaced an optical drive around 3 months ago.
The computer is about 4 years old, but it has been working perfectly until now, never demonstrating any hardware issues. (Or anyway, not that I've noticed.)
Is there any way I can diagnose and fix this?