motherboard : MSI P7N Diamond (NVIDIA nForce 780i SLI Chipset)
CPU : Intel Q6600 processor 2 LGA 775
VGU : MSI NX8800GT in 2 way SLI setup PCI-e 2.0 x16 slot
Sound card : SoundBlaster X-Fi Extreme Audio PCI-e (x16?) slot
Hard drives : 1 500GB PATA 1 500GB SATA
Optical Drive : LG Blu Ray Burner
PSU : Antec TruePower Quattro TPQ-1000
now that you are familiar with the computer here is the problem
i put this computer together about 1.5 years ago and has worked without any problems except this it started with a 530W raidmax PSU and worked fine, for about a day. after just 1 or 2 days when i would turn on the computer the lights, fans, and hard drives would only turn on for a sec, then nothing. but after a few tries the computer would eventually turn on without a problem. this continued for about a year but then one day i could not get the system to fully boot, only get the flashing lights and things spinning up for a sec, no matter how many times i tried. so i replaced the power supply with a 700w by OCZ successfully in march this year and was happy it seemed to be working perfectly. yet i was so, so, wrong. the issue of the computer simply blinking its lights and spinning up only to turn off. but as before if i would try enough times the system would eventually boot. and for some reason i was fine with this. until a week ago i was once again unable to fully boot the computer, i replaced the PSU once again. now with the Antec TruePower Quattro TPQ-1000 a very powerful 1000w psu. but not even a chance to be happy this time. the system turned on once, but without video (i possibly had the cord plugged into the wrong port). when i attempted to restart the system it happened all over again. the system will only flash and spin up, will not boot no matter how many times i try. there have been no beeps or signs that the problem is with the BIOS i have flashed it anyway, but no help. i thought before that the PSU simply did not have the wattage or amps on the different 12V rails for the Q6600 with 2 8800GT's but now that i have a 1000w with 4 12v rails and 100A all together i simply ran out of ideas for the culprit.
any help would be greatly appreciated. thank you for your time
I would guess you abused your MB for so long with a junk PSU that it died, slowly.
Of course, even a good 500W PSU would have struggled with two 8800GTs. You threw badly regulated volts at the modest regulation built in to the MB until that too died. You then replaced it with a better regulated PSU, so the dying components on the board did not have to work so hard, but eventually they just couldn't take it any more.