There are several ways to do this.
The easiest?
Pop in the Fedora install cd #1, or dvd and boot, just as if you are going to do an installation.
At the main boot screen, type in;
linux expert (or is it just expert?).
Run the install until you get to the partitioning menu.
Choose expert partitioning until you get to the actual list of partition(s) on your drive.
Assuming that you have one partition on the drive which houses Fedora, choose that partition--> edit.
Partition the drive/partition as fat32.
Allow the actual partitioning to take place.
Back out of the installation at this point, or remove the Fedora cdrom disk.
Replace the cdrom disk with a full Windows installation disk, reboot and install Windows XP.
"- I'm also aware linux partitions are invisible to the XP cd, which is mainly the problem since the grub loader only shows one possible OS to boot/modify - Fedora."
Yes, because grub is installed to the Master Boot Record on the drive. Re-formatting the partition should solve this. Since you made a fat32 partition on the drive, Windows should now see the partition that you made and allow a full installation.
There are other methods that can work, depending if this fails for some reason, to do the job.
Method 2
Don't tell anyone that I referred to this article!