I'm pretty sure that I know what your problem is. We have one other customer who ran into this problem.
I believe that somewhere in the past, you have installed software from CNET, This could be IdeaBlade DevForce, or some other free download from CNET. To verify this look for a "Protexis" directory in "C:\Documents and Settings\All Users\Application Data".
When we developed the free download for CNET, we added a branch in our Install logic. If there is a "Protexis" directory in "C:\Documents and Settings\All Users\Application Data", our installer auromatically installs DevForce Express without prompting for a key. Otherwise, it asks for a registration key.
To fix your problem, simply delete the "Protexis" directory. Don't worry, it is an empty directory.