hmmmm.....ICit2, I don't think Letang is the brand name of the hard drive. It could be the name given by the virus.
And Flippylumpy, don't panic. I am still hopeful that all your files may be safe. We only have to find a way to get rid of the virus and then recover them.
1. Please upload the screenshot of how your external hard drive looks in Windows Disk Management. Disk Management - Post a Screen Capture Image
(For any other screenshots too, please use the Windows Snipping Tool and upload it. Screenshots and Files - Upload and Post in Seven Forums
2. Was it FAT32 formatted by you in Windows 7?
These just to get the full picture.
Now just do this and report with screenshots.
Shut down your computer, unplug your external drive( if not done already ) and then boot.
Plug-in your external drive while pressing the left Shift key so that autorun is disabled
Now run WinRAR and explore your external drive with it.
Post a screenshot of the contents.
( You may find autorun.inf file and other virus files which you need to delete selecting all those. But first let us see it.)
Well, I have done quite a bit of research on your problem and have chosen this as the easiest and best way to get rid of the rogues. If it does not work, we can try other methods.