Cant access my Hard Drive

I have a 500 gig hard drive that was working fine until about a week ago, now i cant access the hard drive, but it is still showing up in Disk Utility.

I have tried to repair it in Disk Utility but it comes up with:

Disk Utility stopped repairing “Hard Drive” because the following error was encountered:

Filesystem verify or repair failed.

Any help would be appreciated

Thanks

More detail info on the attempt at the repair.

Verifying volume “Hard Drive”
Checking Non-journaled HFS Plus volume.
Invalid node structure
Invalid B-tree node size
Invalid node structure
Invalid B-tree node size
Volume check failed.

Error: Filesystem verify or repair failed.

You got a failed hard drive there. DiskWarrior may fix it but at $100 probably better off investing in a new drive.