Oh, right; 9.1 doesn't have the option on system/preferences to unmount
drives anymore.

just use "sudo fdisk -l" to see listed/available partitions and then I
believe it is "sudo unmount /dev/sdx1" to make sure your internal hardrive
is unmounted. Substitute the "x" for a,b, etc... whatever that drive is
called, and replace the 1 with appropriate numbers of the various partitions
that may show up..