I am not sure, but I would say yes, accept the option to unmount the drive from the Linux install..
--the only thing that is likely to happen if it cannot use the drive unmounted is that it will say so, and stop the install..You'll notice that the unmount is for /dev/sdb*
--one can presume that /dev/sdb* is the unallocated free space provided by the windows partition manager, but that it is currently under windows control, as that is the loaded OS..Vista is on /dev/sda*
, so it is not even touching the Vista drive at that point
I would also review some of the links given so far, particularly the apc mac dual boot vista with linux guide, before stepping into it, unless you feel comfortable enough already..http://apcmag.com/how_to_dualboot_vista ... talled.htm