Windows HP Media Edition. If you know it's not compatible, I'll forget the Upgrade idea. I have 2 legacy programs - an AB dating from 1988, and Quicken dating from 1992. I guess I could do a dual boot setup for those - actually would use Win 98 if I did that. I haven't checked Win 7 (pro or equivalent) which would be my choise of a new OS. Not interested in Win 8 except for smart phone.