NMM Auto Detect Existing Mods

[Pykmi]

The title is very much what I would like to achieve, but I'm not sure if the program can do it. The gist is, about a week ago, I got a new HDD and with it a new OS, Windows 8. I was able to retain my old steam installation, and with it, all my old mods. I can play Skyrim as I did before and all works fine, except NMM no longer recognizes the mods installed in the previous OS.

 

Is there a way that I can tell NMM what all the old mods were that were installed, so that I can, if I wish, uninstall them without having to manually go and start deleting files?