Fortunately this is a problem that is easily fixed. You can fix it one of two ways.
1. Place your win - xp disc in the cd-tray, and run reboot and click on the win-xp setup boot up menu. Then let windows think it is going to reinstall the os, put your cd key in and glick continue. It will collect the info, and reboot a coupl of times, finally it will ask you if you want to install windows xp, or repair the installation.
simply let windows set up repair your windows and this will go away. you will not lose any data or settings by doing the.
I just did this this am, to fix the search companion when it lost files. I know it works!