i was used both redhat linux 9 and Windows XP professional edition,. unfortunately i want reinstall the winowsXP in their partition. then my MBR has been changed. now i only get the WindowsXP.. how can i reload my linux

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
and
type
or

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)

aah..

If you still have problems, post!!!! I'll b happy to answer it...