By the way, I am running WMP 12 on a Windows 7 computer, so if Ric needs any Win 7 specific info, just rattle my cage.
The mysterious E: drive is a creation of WMP to help it keep track of what it is doing when it is Ripping music. It is like making a list to go to the store. WMP stores bits and pieces of file information in that E: drive space to speed up the process. We
mere Users are not expected to even know it is there.
When you say you backed up with separate filenames, on my end I am thinking, of course you did, because there is no other way. All files need unique filenames or Windoze gets really confused.
So, did you make different Folders?
Too much information, but these files were ripped as .WAV files, they should still have Album and Title tags. They can be sorted by Album and by Artist in WMP. That may make it easier to restore your Playlists. But I fear that you need to do that manually.