I was having a problem with an ATI Radeon X1550 video card, and found some discussion on the topic here as well as other places. I just wanted to post a fix for this problem. Forgive me if it's already been mentioned and resolved.
The ATI Radeon video card has a DVI and a VGA port and I hooked the monitor into the VGA port. upon installing the drivers everything was fine until reboot. XP loading screen would come up then I'd see the mouse pointer, the poof! black screen.
I booted into safe mode and found that under the device manager and "display adapters" the ATI software drivers installs drivers for BOTH the DVI and VGA ports, so you have 2 sets of drivers which conflict with each other. whichever one you're NOT using, simply right click on that and "disable" the one you're not using...in my case the primary. (the display adapters come up as primary and secondary) This solves the problem.