I've had problems with dual booting XP. If it was pre-installed, there is usually a hidden partition for Recovery/Rescue, and this messes up the partition count. On all my dual boots I put GRUB on the MBR of /dev/hda.
This is how I have fixed it before.
You will need a CD or other boot disk to get started. The 1st CD of the Suse set can help, also a Ubuntu/Kubuntu Live CD. I also have a Linux tools CD called RIP which you can get
here
Once you get to a prompt do as follows:
Note: My Linux root partition is /dev/hda3. Replace this with the partition for your Linux - /dev/hda5 ?
Code:
#> mkdir /tmp/hda3
#> mount /dev/hda3 /tmp/hda3
#> mount --bind /dev /tmp/hda3/dev
#> mount --bind /proc /tmp/hda3/proc
#> chroot /tmp/hda3 /bin/bash
#> grub-install /dev/hda
#> exit