Thanks for all the replies! I've now successfully managed to install MorphOS, OS4.1, and Debian on the same system. I didn't try Debian Squeeze, though, because of the problems mentioned in the other forums. I just went with Lenny because I really don't need to have the latest version. Lenny is fine.

One more question: Is it possible to mount my SFS partitions in Debian? The Wikipedia page on SFS says that Linux supports SFS in readonly mode, but in Debian I can't seem to get it working. Also, can MorphOS read ext2 partitions?