Empty USB hard drive shows 81% full

[Guy Fraser]

I have emptied the trash, run "sync" and rebooted.

$ sudo ls -la /media/SHUTTLE
total 12
drwxr-xr-x  2 guy  staff 4096 Dec 31  1969 .
drwxr-xr-x  6 root root  4096 Sep 23 17:04 ..

$ df -h /media/SHUTTLE
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2             5.3G  4.3G  1.1G  81% /media/SHUTTLE

I put the drive in a windows box and it indicates 
that the drive is in fact empty [5.3G Available].

What's up with that?