I've recently replaced my old PC with WIN98 with a new Pc with win XP. At first I set up 2 user profiles, (ie At start up win asks which user wants to log on). I then decided that I didn't need 2 log ons so deleted one of the users. Now I get this message when I boot up .....
"Windows cannot load the user profile but has logged you on with the defalt profile. The system has attempted to load or restore a file into the registry but the specified file is not in a registry file format"
Try rebooting the computer and pressing f8 (or if this just gives you a boot menu ,then use f5)--you want the screen that gives you access to safe mode. From this screen select "last known good configuration".
If this does not work and you have a full xp disc then consider a repair install.