Hi davidber,
Unfortunately I suggest you to open a support ticket and ask for a refund. The message you received is one we display when we check the registry on your PC. In some cases, GrimeFighter determines that it should not run to avoid any potential issues with the registry.
We are going to be adding a feature in the early 2015 that will make this check on the PC before offering GrimeFighter for purchase. That way we will avoid the situation you encountered where you received this error message post-purchase.
Very sorry this has happened and post back here if you have any issues with the refund.
Thanks,
davidek