[Unable to uninstall Avanquest PowerDesk Pro receiving "error 1935"]

I have a fully updated Win 7 Pro computer in good shape, but when trying to install an upgrade to version 7 of PowerDesk Pro, Avanquest required that I uninstall the existing version, and I have been unable to install version 8.5 or to get any effective help from support. I get error 1935, and while I have followed every suggestion offered, by support and MS, all that has changed in the component that is included in the description. Any suggestions?

If it were not so much trouble, I would ask for a refund and reinstall version 7, but the serial number no longer works, and expereince indicates that it takes hours on the phone to fix that.