Upgrading comps under XP

I’ve had several occasions to upgrade computers after the user has installed XP due to performance issues. Some have involved new motherboard/cpu combos. On a new motherboard install, XP tends to hang during boot, even in safe mode, with no error message and no apparent way to address or even troubleshoot the problem- just sits there forever on a black screen. Does anyone have any suggestions for finding out what it’s particular problem is? Under any Win9X system I can make anything work given enough time and Internet access, but XP/2000 is frankly a pain to upgrade under.