Hi Ed,
http://www.hitechanswers.net/hipaa-meaningful-use-compliance-windows-xp/You and others may know that a patient's medical info on a win XP machine after April 8th, and even a XP machine on your network, would be a HIPAA violation. Probably won't be caught, but criminals are waiting to release exploits after April 8th. It's the fines that are so dreadful if info is stolen, much less the notoriety of making the evening news for a few nights.
7 weeks from now is not a lot of time, especially with your comment about so many old computers, probably all XP, which is why I add this post.
To try to be helpful, after you get your new server running, do the win 7 upgrade, and make it a backup server.
