I have responded to this request via email previously. I am not sure if you have been receiving the emails?
I am the support engineer that is investigating this issue you have raised. Are you able to clarify something for me? Are you interested in upgrading SQL Compare or just your OS?
With regards to OS you can use the 'Win 7 upgrade' version to upgrade from previous OS. The simple version that is titled 'Windows 7' will do a install that will be a clean install.
Thanks for your feedback in this matter.