Format new msdos drive
To create and format a new FAT32 drive do the following:
Go into sysinstall
use type 11 (fat32)
# newfs_msdos /dev/da0
Note when I went to do this on a IDE drive on ad1 I had to do
# newfs_msdos /dev/ad1s1
Now you should be able to mount it as msdos.