1. Insert the Windows XP CD-ROM into the CD-ROM drive, and then restart the computer.
2. When the "Welcome to Setup" screen appears, press R to start the Recovery Console.
3.. When you are prompted, type the Administrator password. If the administrator password is blank (you didn't set one), just press ENTER
4. At the command prompt remove grub by using the command: fixmbr
5. reboot and windows should start normaly.
(thanks to sailor at www.fedoraforum.org