An unformatted drive does not show in EXPLORER. It needs you to make a partition and format that in XP's Disk Management tool.
I have a minor problem I had a Samsung 200g HDD (unformatted) that I put in a USB caddy and plugged it into my XP machine. But window?s doesn?t recognize it. I go to My Computer and all I see is are the Internal HDD. I know the USB section works I tried another HDD (formatted) and it shows. Could the drive be DOA?