Imageing makes a exact copy of the system . . warts and all . . If the system is messed up, that may not be vdery useful.
You can easily copy any data you cherish to external media and restore that once you have a stable and protected system
This is a good guide to reinstalling XP . . you might want to print it for reference during the install.
http://www.techhandbook.com/windows/3078-Guide-Installing-Windows.html
