Vista - SCSI + IDE + Backup

My computer has several SCSI drives and one big IDE drive. The IDE
drive is intended to be used to make backups to.

When I installed Vista, Windows was placed on the SCSI drive I
directed. But the system partition was put on the IDE drive. Same
thing happened before, when I had XP. That was no big deal, because
it didn't affect my backups. But the Vista "backup program" doesn't
want to let me backup to the IDE drive, presumably because of the
system partition.

What to do?

- Tom