No other details? In general the drive would indicate "unallocated space" where Windows cannot detect a (File System) format.
Are you seeing this: if so send back your screenshot:
Did you run Seatools? This is the only way to know that the hard drive is mechanically functional.
If none of the above help then you need software or hardware outside of Windows.
Most software recovery products allow a free scan but cost for retrieval of data. Usually @$100 or so.
Most hardware recovery goes into @$1,000 plus.
Here is a Google for the softer side:
http://www.google.com/search?sourcei...+data+recovery
Also in the future remember to backup any important data to more than one hard drive.