If you have installed Windows Xp again...then you just need to install GRUB (The Boot loader) again...
The procedure is quite simple.
Put your Redhat Linux 9.0 CD 1 in the Drive.
Boot your computer
type "linux rescue" [Press Enter]
Follow the onscreen instructions where it will ask for language,keyboard configuration and certain settings.
Once done, you will finally see a message of regarding "chroot /mnt/sysimg"
and will say to press something to continue to with the CONSOLE
Just change it to root login at that time
the former is recommended.
If there is a positive acknowledgement (or rather message display with successful installation of GRUB) then all done!
Remove the CD and reboot by pressing CTRL - ALT - DELETE (or reset button on CPU)