How do I recover data that I had on a external hard drive using usb that I accidentally unallocated the data doing a clean install of xp.

I decided to do a system restore on a xp machine, I had a external mybook 80GB plugged into it. I used the xp disc to do a clean install. When I got to the part were delete partitions , I didn't realize that I still had my external drive plugged into the pc and I deleted the partion at the same time. I noticed it right away so I unplugged the mybook,  Now when I plug the my book into a working system no drive appears, I believe that is because it hasn't been reformatted . How do I recover the data files from the drive. I am not sure if it was a fat or ntsf file system on the external drive