suggestions on what could be wrong with my PC

sometimes my PC boots fine, sometimes the fan and harddrive light come on for just a second, then everything shuts off.
Any ideas on what could be the problem?
thanks
Answer #1
from my past experience the reason its failing 90% time, is due to your power supply (PSU).
1) Either you PSU does not meet your motherboard voltage requirements. (that’s why it cannot power all your devices) In that case upgrade your PSU with higher watts. 2) The PSU, has not been connected properly, so make sure all the cables are setup correctly.
3) The PSU is faulty, in that case replace it with a new one
Answer #2
Agree with
My money is on the PSU as well, check your connections though
Answer #3
Some info on your computer would be nice, description of the parts (brand, model).
If a mate is close to you, could try to borrow his power supply for a test. Some computer shops will gladly diagnose for free.
Answer #4
try doing a BIOS reset with the motherboard “RESET_CMOS” jumper
or try disconnecting the power and remove the mobo battery over nite to rest the BIOS
you change anything just before this started ?