There can be problems with uninstalling Fedora Core and installing WinXP, as the Windows installer is broken and has problems installing over existing Fedora installations.
Run the command: dd if=/dev/zero of=/dev/hda bs=1058576 count=100 (where hda is the master boot drive). This will erase the first 100mb of the disk, making the disk look clean, so other installers can work.
Reboot the computer, boot from another boot cd/floppy to install a different operating system.
