http://filehippo.com/download_recuva/
Try this on it... Sounds like it just formatted the whole drive to one partition. Take it to a friends house and plug it in to see if it can read the old partition.
Also, I recommend a small 80GB hard drive to keep your OS('s) on and leave no important data on it. When you reformat you pop your data discs out and leave the only real one in.