First of all my system:

hiper 580w PSU
ABIT AN8-32X MB
3gig Ram
AMD Athlon 64 X2 4600+ CPU
Sapphire radeon x1900xt GPU
Samsung SpinPoint T133 300GB SATA2 8MB 7200RPM HD

when I turn on my pc, it seems like its an ordinary boot-up. But the GPU fan runs at full speed all the time and the screen stays black, in fact the monitor never turns on at all (when its working the fan starts at full speed, but slows down after the screen turns on). i started having this problem after i moved my computer some months ago. I buildt it myself about a year ago and it worked flawlessly for months, and didn't have any problems at all before i moved it. I checked everything inside the case and everything seemed to be as it should, but it still wouldn't start up. So I took out everything and buildt it from scratch again, but the problem still didn't go away. Then i got a little bit angry out of frustration and smacked the computer a few times on the case. oddly enough, this time it started up like it should. But if I accidentaly bumped the table the computer would freeze and the only way to get it to work again was more violence . For the last couple of months it has worked like it was brand new again and no violence was needed at all. But today after i bumped my table, its the same old, where it refuses to turn on the monitor. I'm sick and tired of turning the system on and off, hitting on the case inbetween startups and still dont getting any response. So anyoney got an idea of what can be wrong?

loose connection somewhere ,if reacts like that to being jarred ,loose power plug to the board or hdd ect ect .,or add in cards,like ram and video ,modem/sound ,you really should not be hitting it to make it work only making things worse as you know!