Is the drive removable? i.e. can you get it out of its case? It might just be that the controller is dodgy.
Alternatively you may be able to recover some of the data by mounting the drive in Linux and copying it off. No guarantees it will work though. Something like Knoppix should do the trick.
It could be that the MBR is goosed, in which case there are fixes in Windows, but you risk losing your data.
Failing everything else, if the data is that important to you, there are data recovery companies that can rescue it for you. It's not cheap mind.
Start with the simple stuff though.
like samdy says, there are companies that can do it for you, You can format a HDD 6 times and the data will technicaly still be there and with the right equipment still recoverable.