reboot at desktop

ok guys, this has me completely stumped. I just put my bros comp together. It also has a gigabyte Ga-7DPXDW motherboard. Well, yesterday it ran fine for a solid 18 hours.

Today, after about 2 hours in i guess the monitor goes black, and all the LEDs on the computer light up. Hard drive, CDROMs, everything. So i tell him hold the power button to reboot. It wont.

Now, everytime it just reaches the desktop, it goes black. No partial BSOD or anything, just black.

I havent the slightest idea, i really dont. we just sent 1 stick of ram back from this batch, but i dont think thats it because theres no BSOD or errors or anything. Im going ot try knoppix and see what happens.

Thanks in advance.

Some of the dumbest problems i've seen that cause such things are out of range resolutions/refesh rates.

A few things you should do first:
1. See if the machine comes up in safe mode, if it does that is a good sign.
2. Try a different monitor, a larger one is the best.
3. Remove drivers for video in safe mode.

so far what we did

1. ran knoppix for a good 2 hours, NO problems. looked damn nice too.
2. hooked up a 15" trinitron....worked great....up until it went to "sleep" it crashed.

so we think this is a video issue? wouldnt surprise me, that card thats in there is my old SiS, the direct draw and ogl died (explain that one) i have an nvidia 5700LE i coudl probably throw in there since my dually passed away...and im moving to mac..but now i hafta help my bro

well, ran knoppix, no problems..checked the vid card, it says theres a second monitor conneted, when theres not. i sotpped looking at the vid card once we got a ton of bsods with "error, page fault in nonpageable disk" which points at the memory.

running memtest now. no erros, but its frozen twice.