You can take the drive out, hook it up to another PC running Windows, and try dskchk <drive letter>:\ -f -r if it shows up in Computer. I've had varied success with that, mostly inability to read, but there is that off chance. Otherwise, you could try a professional data recovery service, but it will cost $250 USD at least, and they don't guarantee success.
How important is the data (and more importantly, why weren't you running regular backups?? Bad user, no donut)