Drivers. Make sure you have downloaded all the current ones availible for your peripherals, even if updating from 2k or NT4. Some of the off brand hardware has problems with the generic drivers included in XP. Also be aware that if you burn cds with Adaptec, you'll have to go to their web site for the XP patch to createcd. For some reason I lost all burner capability when I upgraded. Adaptec wants the registration number for your current CreateCD before they give out the patch, so have that handy. Once it's up and running though, the OS is pretty stable. Hope this helps jbear