This isn't so much a problem, it's more a curiosity...
I have 2 hdd's (hda, hdb). On hda, I have a gentoo linux system installed. On hdb, I have windows xp. Grub is installed on the MBR of hda.
When I installed XP, I had to disable hda. XP wants to be the dominant OS and wouldn't let me install it to anything but the primary hdd. Whatever....
Anyway, the xp bootloader is presumably on hdb's mbr. So when I set up grub.conf, I did the following:
Grub didn't like that. When I boot it, there is an insane beeping that only ends with me hitting the reset button. I've tried varying the root option by doing "root (hd1)." I've tried other variations after consulting Grub's man page.
Personally, I wouldn't think xp's bootloader being on hdb's mbr would be a problem. Normally windows overwrites the primary drive's mbr when it's installed. And when you install Linux you wipe the mbr again and replace it with lilo or grub.
Anyway, as I said, it's not really a problem, more a curisoity than anything. I have access to both os'es anyway. I just like using Grub more than my computer's built-in hdd boot selector.