What do you exactly mean?
My LILO was on my second HD (hd1) and both XP and Mint are installed on partitions of the first HD (hda1 and hda5). This was also the case when I had Mandriva. On the second HD, there are only data. It might look weird to you, but I found it convenient to let the MBR of the master disk as is, just in case (imagine Grub doesn't work!). It worked just fine with Mandriva.
From what I understand of your post, you suggest Grub needs switching the HDs? I read some posts on this topic, but I don't think it's the problem since :
- when I boot from first HD, XP runs OK
- when I boot from the second HD, I have this GRUB black screen, sio I guess it is found.