Upgrading a system from FC1 straight to FC4 is really too much of a jump. Remember that if your /home directory is on a separate partition then you can run a full installation and have the installer not reformat the partition.
You can also choose in the install process to not reformat the XP drive, and set the boot loader to have Windows as a second option.
If recovering the data is vital then I would probably unplug the drive and pack it away until that was done - software does exactly what the human tells it, even if the human makes a mistake