It should not-- The only thing it should rebuild is the Master Boot files.
If you are leery-- you could do the old take the drive-- slave it to a known good XP install-- on a friend's (?) PC-- and copy the files you must save to CD-rom. This is where the "backup" admonition you alway hear comes into things...
There are all kind of links to many resources from that article-- scroll down...
above all be patient read all you can.