insert the windows xp installation CD and delete all partitions. that will wipe everything off the hard disk. then do a fresh installation of windows.

you do this by restarting computer then boot from CD, go through the menus to install XP fresh not repair, and then delete all partitions so you have x amount of unpartitioned space then create 2 partitions. One 10GB for windows and the other x amount of space for all your data. best way.