Hello,
I have a 3 year old pc, which has lately shown a very weird problem which i was not able to find a solution even on a search engine.

Whenever i log off from my windows user account or restart my pc, my computer just shuts down after reaching the log off screen as if it was a power cut. It also goes off like this when my computer hangs up (which should usually show a blue screen of death).

Now after this, when i start my pc, i hear the fan spinning and the power light on the CPU Cabinet turns on for 2 seconds and it suddenly goes off. This continues for 5-6 times and after that, my pc starts normally.

This failure of booting only occurs when the pc goes off on its own, i.e., when i start my pc in the morning (after its been off for hours), it starts without a problem.

I believe this is a hardware problem since I've Windows XP and Ubuntu installed on my pc, and before loading start up programs, my pc is supposed to ask me which OS to start with, but it doesn't when the computer fails to boot.

Hope you can figure out what the problem is