Oh boy... I'm not in a good position to try to support a Windows XP system Release with very old FocusMax (which isn't even my software). First I would try to reinstall FocusMax V3. I don't have the installer. However I found this site which has the old free versions.

https://www.astronomylog.co.uk/focusmax-downloads/

With that said, I would really recommend you get your OS and software up to current.