hmmm, let me get this straight: FreeDos is installed? Then your harddrive does have at least one partition: the partition that contains FreeDos. If you have installed Fedora, than there's at least one partition, too: the partition Fedora is installed on. Neither of those partitions (providing you still have both Fedora as well as FreeDos) can be used by Windows.
Chances are you need some free, unpartitioned space on your harddrive to install XP. Problem is that you've gone about it the wrong way around: you should have installed XP first, then Fedora (if you want to keep Fedora, that is). Reason for that is that Microsoft simply does not support non-Microsoft operating systems in a dual boot setup.
So think what you want, and how you want it:
- only XP? No problem, format the harddrive completely and install XP
- Dual boot XP/Fedora: remove all partitions using the XP boot disk, install XP in a partition, install Fedora in another partition (make sure you don't let XP take up all space when formatting).
- Triple boot XP/Fedora/FreeDos: install XP in one partition. Install FreeDos in a different partition. Install Fedora in a third partition.