Booting problem :/

Hey all, been having some trouble with my comp, its a HP Pavilion Media Center m8000 Desktop PC, has a GeForce 9800GTX added to it

had some trouble with it before, computer locked up when I left a game running overnight, wouldnt start and I had to put in a sata card to get my hard drive and cd rom to work because I think my sata ports were bad, that was about six weeks ago and it started working fine again

then after working fine for a few weeks i had a windows update and when it went into sleep it wouldnt start, and I'm getting a blank screen again..

I've tried reseating everything and booting it with just the bare bone equipment, tried ram sticks individually, tried the on board monitor plug, none of it worked

then I tried it after it had been off for a few days.. normally the sata card shows a red power light for a few seconds then goes off when the comp fails to boot, after a few days of not trying anything i turned the power switch on the surge protector (had been off) then turned on the computer and it worked! also, the light on the sata card stayed on.. unfortunately, my usb mouse and keyboard did not work wihen I started it up, and when I reset the computer I was back to the blank screen. Since then, i reseated everything and redid the stuff before, but to no avail..

I did notice that if I unplug the 4 pin 12vATX connector beside the cpu, the sata drive will stay lit up but still nothing on screen, and the fans power down after about 5 seconds

hard drive spins up, usb stick receives power.. wireless modem usb stick doesnt turn on, but did that one time it worked..

still kind of a noob but I've tried everything so I know so please any advice/help ty!!