Hi bolandorders,
Please open a ticket with our support team to get a refund. Because GrimeFighter looks into all the deep corners of your PC and tries to clean all the junk it takes a very cautious approach to doing that if it sees anything in the registry or otherwise that might somehow cause issues with your PC after it runs.
Because of that, you have received this message. It isn't necessarily your OS but more registry or disk configuration.
We should be releasing a new build of the product in mid-Feb that checks this status before presenting the initial offer to users. That way, we can determine if we can run the product on your PC or not before you purchase it.
Best regards,
Davidek