SYS: is automatically assigned to the device you booted from. So make sure you didn't boot from the Asim floppy.
The other issue that Thomas alluded to is *too much* space on a partition. Older versions of Installer, which I suspect Asim is using, get confused if more than 2GB of space is available. Simply change the default tool of the install icon on the Asim disk to point to the version of Installer on your hard drive (either in C: or SYS:Utilities). The 3.9 install should have put it there for you.
Finally, make sure you're using Asim 3.10 and not an older version.