I've not been using FreeSCI... would that allow the games to run in full screen under XP?
I've heard that a lot of people have trouble getting the games to run period... for me, they all run perfectly, just in the small window.
I also have a machine running Windows ME... the games run in either full screen, or not at all ( the VGA games all want more memory... even though PCs in that day didn't have near the amount of RAM that newer ones have.