Long time ago I installed XP to /hda. I received new hdd and was planning to install also linux to new system drive, beside XP. So I installed first XP to /sda and after that also centos to /sda and configured GRUB to install at /sda as well.
As I reboot, centos boots fine but XP doesn't load at all. Then I figured out that XP installed its boot loader to the old system drive /hda where old XP system was installed. Really bummer, how stupid it can get :/
My question is, what would be the easiest way to get my new XP from new drive to load with GRUB.
One option I thought would be to de-attach old system drive, install new XP once again to new drive. This of course would destroy GRUB on new drive and then I would need to figure out how to reconfigure or reinstall only GRUB. I do not want to re install centos again, which is running smooth.

Thanks a lot!

What about you detach your hda from the computer, fixmbr from windows CD's recovery mode and resetup grub?

You should not need to reinstall grub. Try editing /boot/grub.menu.lst. You will need something like

title Microsoft Windows XP
root (hd0,0)
savedefault
makeactive
chainloader +1

You need to reinstall grub only if you fixmbr.