My computer set up for the past 2 years has not changed, and is:
 
AMD 64 3200+, 2Gb DDR, Asus K8N-E Del, Primary HD 80Gb Western Digital, Slave HD 160Gb Western Digtal (model number WD1600JD).

I use my primary harddrive for windows, and the slave for my documents (currently about 60gb worth over 6 years).  
 
The problem is on my slave harddrive, the WD1600JD. Both drives connect through sata and have never had any problems to date.
 
Today, my slave drive would not open when in windows. The drive shows in the BIOS, it shows up on the device manager and even shows in 'My Computer', however when I try and access the drive the following message appears:
 
D:\ is not accessible
The file or directory is corrupted and unreadable.
 
I have taken the following steps:
 
- Dis-connected all cables to the drive and reconnected
- Uninstalled drive and restarted windows
- Taken drive out and tried to load on a diferent computer
- Ran Western Digital diagnostic software which the drive has passed
 
Still, the drive is un-accessible. I am beginning to fear the worst, as in disk management it is showing my drive to be 100% free, which is not the case as I know I had over 60gb on there.  
 
The only thing that has changed over the last week is access to the drive through my Xbox360. I updated the PC to Windows Media Player 11 and the Xbox 360 shared the relative documents, for one day, until they could no longer access this. Now, the only thing that came to mind is something to do with the sharing rights of the drive has triggered it to become inactive as maybe it considers the Xbox360 a risk to share with.
 
However, this is unlikely. As I said, the problem came about today when the drive could suddenly no longer be accessed through windows.
 
Please, can anyone help me try and salvage data if not the drive. I am about out of ideas of what to do.

Get a data recovery program, like Getdataback and try to recover your files.
Spinrite is great also.

Have you tried running scandisk on it?