When I first bought/downloaded this game, (maybe 10 yrs ago) one of the admins told me of a site where you could get fixes/updates/cheats etc. by donation. Recently got a new computer running windows 10 and can't get the game to run in full screen mode (or with taskbar on top). suggestions?

You want to pay for patches???

I suggest the HD mod to fix your problems. For free.

where do I get that?

https://sites.google.com/site/heroes3hd/

And you can even donate.