As root, try it like this:

# mount -t vfat /dev/hda? /mnt/hda?

-OR-

# mount -t auto /dev/hda? /mnt/hda?

You need to make sure mount points are defined in /etc/fstab if you want the easy mount commands like so:

# mount -t vfat /dev/hda?

You can't mount a drive into thin air- it must have a mount point. Also that mount point must exist in the directory /mnt.

Do this:

cd /mnt
ls

That will list all of your existing mount points. You can mount any drive to any mount point like so:

# mount -t auto /dev/hda1 /mnt/cdrom

Oooooooh now that's just insane isn't it?