firstly I am trying to get rid of that answer and hope people find this
http://www.linuxquestions.org/questi...troubleshooter
can you post your /etc/fstab file for linux and if you have not xp in that file what each C drive is on for hda
eg hda is partition 1 first C drive part 2 is its swap part 3 is second XP
2) you have multiple choices with 2 mbrs. If bios boot order is hda then hdb (xp then linux) then grub can go into mbr for hda or boot order changed to hdb and grub into that mbr or as per above link you keep ntloader in hda and chainload grub which is put into the PARTITION of linux /boot
we need more info to help you out if you don't understand what I just said.
3) to begin with have a look at the keep windows bootloader section of the link and see if that appeals.