Ubuntu Installation :: Booting From An Alternate (pre-existing) Partition?

I can't boot to Windows XP after recently installing Ubuntu (Ubuntu boots fine). The error that comes up (straight after selecting XP) is that it can't find "system32hall.dll".

Reason for the problem: Ubuntu is looking at the old, corrupted version of XP that I have. The 'real' version is on another partition, for reasons too lengthy to explain. Note: neither of these partitions were touched when installing Ubuntu - I placed Ubuntu in the pre-existing partitions I had setup when installing previous versions of Linux (last was Mandrake 8.)

Now, I can understand why it is looking at the old version, because it is on the first partition of the hard drive, "dev/sda1", the new version is on "dev/sda3" (nomenclature according to Ubuntu, obviously).

Question: How do I point the config file to sda3? I have tried setting root to "hd0,3" and "hd3,1" with no luck. Original code is below:

Code:
### BEGIN /etc/grub.d/30_os-prober ###
menuentry "Microsoft Windows XP Professional (on /dev/sda1)" {
insmod ntfs
set root=(hd0,1)

[Code]....