XP here. I agree with my fellow users who urge you not to spend a great deal of time making the FPSC work with significantly older versions of Windows--at least not as an immediate priority. But this is not because I have little sympathy for them. Believe me, I understand using last half-decade's technology or operating system and being unable to upgrade. Been there, done that, could write the freaking book on having a big want list and no cash. They do have my sympathy, but so, too, do your other VERY LARGE group of users.
Yes, what concerns me is the huge bug list for your 'cough' OTHER flagship product . . . you know . . . just a hint; it goes by the name of DBPro. It would be nice if your team could spend, oh I don't know, a day or two to fix some of the things that people have been complaining about for a very long time, that are driving them collectively batty, things that something labelled PROFESSIONAL ought not have as problems. Just a suggestion though.
Your pal Opus [ducking and running for cover--don't hit me!]
Eternal student in search of knowledge. But will settle for the occasional epiphany.