The two commands you are looking for is and if your bootloader has been altered. However, I'm not sure I understand you question.Both can be accessed from your windows xp cd recovery console.
But first you gonna do this first :
and check out if your entry for windows is correct. Is it pointing to the good partition?
sudo gedit /boot/grub/menu.lst
Remember this: Windows likes to be on top. That means, it likes to be the first OS installed on a system and likes to be the first partition of the disk (ex: sda1). If that's not the case, you might wanna fix that first.