Split-Screen at Boot in Win2K

I have a remote user who is reporting that when Windows loads (just prior to the login screen), her entire Windows desktop shows up in duplicate; once one the left half of the screen, and once on the right half of the screen. Of course, it’s so compressed, it’s impossible to get anythign done. It doesn’t happen in safe mode. Video card is ATI, monitor is a Packard Bell (but no monitor shows up in DevMan). Ran hardware discovery, found nothing new. Any ideas what could be causing this, and how to fix it. “It worked fine for me,” before I shipped her the CPU (monitor is hers).