When the screen goes black, does your entire screen go black and are forced to push the reset button?
Maybe your processor overclocking is causing the video card to not get enough voltage. You also may be required to get a higher watt power supply for your video card. If you have a Radeon, this may be the cause, combined with a limited power supply. All Radeons seem to hog the +12V rail.
I remembered, but not occuring with my newest motherboard, when after I plugged in a Radeon 7000 video card, with two hard disk drives attached, everytime I attempted to access the CD drive, the screen went black and I'm forced to push the reset button

.
Then I decided to enter the BIOS setup utility to check the voltages with the Radeon 7000 video card installed and found out in shock that the +12V rail under no load only at 11.4V, thus probably even worse when under load at probably only 10V!!!
When I unplugged my second hard disk drive or put my GeForce 2 MX200 video card back in, voila, my PC didn't crash when accessing the CD drive.
Does the PC lock up with a black screen when loading *any* 3D game, including PC-ported games? If it does, you are required to stop overclocking, change Vcore or back down the processor frequency by -50 mhz.