Uninstalling (for the most part) is simply reversing the installation method. For example, if to install it you used:
sudo apt-get install ndisgtk
Then to uninstall it you would use:
sudo apt-get remove ndisgtk
There are additional details you might want to read:
The last link deals with the windows wrapped drivers that are created in
That said I'm often one of those "Leave well enough alone" guys and even if I wasn't using Windows Wrapped Drivers anymore I might be tempted to just leave them be. On the other hand if
dkms was compiling the new drivers with each kernel update and the time was distracting me, I probably would purge it all.