Won't turn on

My computer wont turn on. D:
I press the button, nothing happens. Sometimes, it lights up, but shuts down again immediatly. Is it the powersupply?

HLEP ME D:

>>8

You forgot:

4.  CPU Fan is dead and the system is automatically shutting itself off to prevent damage to the chip.  I had this one with the shiatty fan that shipped with my 1900+.

>>1

Does your cpu fan spin freely?  If not, the bearings may be shot.  This is good news for you b/c that's a quick&easy $10-$30 fix.