Re: Another dual boot thread!
If the Windows XP Professionial CD will boot normally with Fedora present on the drive, then go ahead and re-install XP. Then, as you said, re-install GRUB. There are several methods to do it, but the classic way is to boot with your Fedora DVD. Choose "Rescue installed system" and follow along until you can choose to start the bash shell. Then enter chroot /mnt/sysimage. At the next bash prompt, enter grub-install /dev/sda to re-install GRUB in the master boot record of the first hard drive.
P.S.: Don't change the existing partition layout when you re-install XP. Re-install XP right back into its old partition if that works for your purposes. Otherwise, you may have to do more to Fedora than re-install GRUB. If you must tinker with the partition layout, you probably will be able to get Fedora going anyway with an additional config file edit or two.