Upgrade mb on hp pavilion 4400 desktop

[obscure02]

what mother board will the case take. Hardware memory card readers fine. 250 GB HD adequate. What newer MD with processor video card and extra RAM can be installed??

 

[obscure02]

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.