I helped someone else out in the exact problem as you.
I'll give you the information. You're definitely welcome to ask questions, but I suppose it's up to you to decide what you want to do.
In his situation, he could boot to another operating system (XP and Vista) to access the drive but under 7, it had 0 bytes.
So I had him copy everything he needs off the drive in the other OS. Then I told him to low level format the drive. After doing that, the drive was read well inside Windows 7.
My best advice to you is to backup the hard drive by any means possible to another storage medium. Even if that means taking the drive out of your computer and placing it in another one running XP or Vista.
Then perform a low level format on it once you are satisfied your data is secure on the backup medium.