the best way to boot win and fedora is to buy a second hard drive rather than shrinking a working fedora( most likely setup on the default LVM)
install the new drive as the FIRST drive .Unplug OR be VERY,VERY careful with the windows install ( by DEFAULT it will reformat your linux drive to windows )
" We are Microsoft resistance is futile , your own...will be add to ...".
There is , on xp sp2, a check box you need to UNCHECK it so windows will only install on the first drive .
then you need to decide how to dual boot
1) use grub to boot both
2) use the windows boot loader to boot win and fedora
in this situation 2 is the easiest
see: " HOWTO Dual Boot Fedora & Windows With NTLoader "