booting up problems

so heres my story, one day im playing a game, then the monitor goes black but the computer is still on; so i restart my computer. the computer lights go on, all fans are spinning but my monitor doesnt turn on. so i thought my monitor was burnt out and to make sure of that, i tried it on the other computer but it surely did work.

i then questioned my psu; its only 300w and i have a x850xt in my computer so i thought it might have finally burnt out or something. i bought a new enermax liberty 400w and hooked it all up and it booted up first try. i then shut it down and tried again and it like how it was before; all the lights are on and the fans are spinning so it surely is getting power. it sounds like the computer is stuck booting up because the fan on the x850xt is loud (loud when it boots up, but then it goes quiet when it does).

an odd observation ive noticed is that if i let everything rest for like an hour, and try again it boots up, but if i shut it off and try again it wont. almost seems like it has to 'charge' up or something.

anyways, im out of ideas at the moment. maybe something got damaged when the original psu went out.

p4 2.4ghz w/t
gigabyte 8ig1000mk mb
x850xt 256mb agp8x
512x2 pc3200 crucial ballistix ram

stock cooling on all

i just tried my old 9600xt and 7000 and still no go. also when i said:



i take that back because its been sitting here for 2hours and still wont boot