Hi,
If this drive does not have any phyiscal problems, then you should be able to get all the data off it using Recover My Files (
Data Recovery Software to Undelete Files; Disk recovery; Recover Deleted Files).
When you plug the drive in as a secondary drive, run Recover My Files, select the Complete Format Recover search (you can follow the instructions in the first post of this thread), when you get to the drive selection window, you should see the problem drive listed as a 'physical drive' (if it does not show up, then there is something wrong with the drive itself.