Linux HDD being used on Windows

If it is a Linux disc then Windows will not be able to read the disc without you installing a driver. Have a look at:

http://www.fs-driver.org/

Is the drive listed in device manager? If you go to Control Panel -> Administrative Tools -> Computer Manager -> Computer Manager and then into the storage options do you see your disc listed there? If you don't mind loosing the data from the drive then you can just format it, it's the Linux file system that Windows is to dumb to understand.

audiovoodoo's reply assumes you need to access the data on the drive. if you simply want to use the drive for additional storage an your computer then you can wipe the existing partition and create a new windows NTFS partition instead.

I think I rather covered that side in my original reply