Ok, here it goes. I have a media center pc that I built about 3 months ago based on the following components:
Antec 300 case
AMD Phenom II 940 @ 3.0Ghz (OC to 3.4)
Gigabyte MA790X-UDP4 rev 1.0
EVGA 8800GTX ACS3 video card
2G DDR2 800mhz Corsair ram (single module)
ATI 650 dual tuner
3x 1.5 terabyte Seagate hard drives
1x 500 Western Digital hard drive
2x dual layer DVD drives
1x Blu-Ray LG drive
5x 120mm cooling fans
Corsair 450 watt psu
Vista 64 Ultimate
About a week ago I noticed my system was getting slow in response time trying to open/close programs and a couple of times I was forced to press the reset button to shut down and restart. It was slow to boot but at least did reboot. About 2-3 days ago I did this and then the boot screen and the motherboard logo screen came up but just prior to Vista screen was supposed to display it was a blank black screen. I notice this once or twice and eventually the OS came up. But the next time after that it didn't.
So now my system gets to the windows logo screen and stops only to display a black screen making you think it might come up but it dont.
What I have done to this point is put a tester on my PSU to see that all is ok. Everything is in spec and looks great. I disconnected all of the power cables and the SATA cables and rerouted and rewired everything. I rebooted and get the same thing.
I have reset CMOS to factory specs, tried loading factory defaults in the BIOS and still no avail.
Lastly I have taken out the 8800GTX ACS3 card and tried another identical card with still the same issue. I followed this check by taking out the wife's 9600GT and testing with that to see if it could be a power supply requirement issue. I still get the same thing. I had also disconnected all drives but 1 hard drive (boot drive) and 1 dvd drive and -1 120mm fan.
The only thing I haven't done is remove the cpu and reseat. I doubt this is the answer though. I have submitted a request from Gigabyte to assist me on this but it will likely take 2-3 days to get a response from them. Gigabyte is a great product but their support is nothing like EVGA's and unfortunately I don't think EVGA has a motherboard that supports this cpu. EVGA has spoiled me with their customer support! Lol.
Any suggestions from any other gurus out there? I have tried about everything seems to be pointing to the motherboard IMO.
I have actually used this calculator already and it recommended the following:
all as listed above 461 watts
9600GT no OC 387 watts
9600GT OC to 3.6 401 watts
My original configuration was definitely at the top end of this psu but the amps on this psu are higher than most 450 watts so there should be a buffer to cover the difference. This psu is comparable to some 550~600 watt psus out there.
It still seems the 450 watt should work although they wont suggest it. Since I'm having issues its possible its a power supply requirement issue. You just would think this would clear up once you install a lower end graphics card and remove most of the drives.
I just input the info using the 9600GT and it suggest the one I have:
Well the the GA-MA790X-UD4P that you have is similar to my GA-MA790X-DS4. Anyway I've previously had some random problems where it was giving odd behavior and then the graphic driver crapped out. Got stuck in VGA mode and couldn't change resolution or use any hardware acceleration. Thought it was the graphics driver but removing and re-installing it did nothing.
Seems that it was something with the chipset driver and corrupting a windows update. Rather than try to narrow it down I just restored the image I had (the install itself was less than a month old) using XP rather than figure it out. I had just found out that Vista didn't have a repair like XP did so that seemed easier to do . The second time I had to restore though I think the south bridge just go too hot and ended up corrupting a windows update (note it's anemic cooler on both boards). Of course, the system runs hot when as it heats up the room so I can't game with the air conditioner off here in West Texas ^_^
Anyway the system seems stable now with an updated SATA driver that you can get on Gigabytes website. For now though I think it would be easier for you to do a fresh install. If you have files on there that you need then I would say download Knoppix and burn the live CD. You can use it to boot up and transfer your files to an external drive or another computer on your network.