God virtualize. I run Debian Lenny 5.1 wit a dual monitor setup with my laptop monitor as the main and an external LCD as the secondary. First step get Fedora running with your dual monitor setup, once your dual monitor setup is working install VirtualBox or possibly even vmware player. Then create a VM using your XP partition as the harddrive (google for tutorials on that one) Once you have your VM setup with the physical partition as the harddrive for the VM boot the VM then place it on whichever screen you want and run the VM in full screen mode, you will have your dual OS setup. NOTE: You will need to install VBOX tools or VMWARE tools to get seamless mouse integration. ALSO NOTE:YOu may have to reactivate windows once it boots in the VM, if you boot between XP on computer and XP in the VM you may have to activate windows everytime. This will soon eat up the limit MS puts on activation. There are ways around it, google for it.
I have enclosed a screenshot of mine, My diplays are configured with the layout of one on top of the other