can't use a system with two hard disks, both with a linuxinstallation?

[Marius Andreiana <mandreiana rdsnet ro>]

Hi

I have two hard drives at home, and one has redhat 7.3, the other
limbo2. Both work fine separately.

However, when plugging them both and starting the computer, I get the
message
mount: LABEL=/ duplicate - not mounted

The problem is clear, I had to remove 1 hard drive, boot the other,
change /etc/fstab to use /dev/hdxx instead of LABEL and then both 
hard drives worked.

How can this be avoided though?
Thanks