[dnanian]

The problem is that the way to avoid erasing it -- using "Copy Newer" or "Copy Different" -- will merge the selected contents of the drives, which isn't necessarily the kind of thing that can guarantee a bootable result...

In general, the only effective way to do this is to partition the drives, or (and this might be easier), copy Myst off and then back on again (perhaps to an iPod or similar)...