Probably the easiest way is to
1. Remove RH (assuming you just installed it so it's no big deal to reinstall it)
2. Install Windows XP
3. (Re)Install RH - at some point in the installation process RH will notice there's XP on the disk. You can then partition the disk according to your needs. When you install grub it will include XP as one of the menu items. On bootup you can choose RH or XP.
The general rule-of-thumb (if I'm not out of date) was: Windows first then Linux = GOOD
Linux first then Windows = PROBLEMS
jdk