I believe that there's a registry edit required to *cleanly* remove SOLIDWORKS, when trying to install a new (i.e.; differently-licensed) version. I don't recall exactly what I had to do, but I found a solution for a very similar problem via Google--and had to do a registry edit to remove the key(s) that SW had placed there. Otherwise no matter what I did, SW thought that I was just trying the same version of it time and time again. Groundhog day, to be sure.
If anyone needs more information, I can probably find a link to the procedure I used before to get this working.
TB