I had issues trying to use Vista. I'm not saying it can't be done just that I had problems with it. I would recomend the use of XP Pro.
I even went so far as to remove the Hard drive from the Vista system I had purchased. Replaced it with a new clean drive, formatted & installed XP Pro. Then I found I had issues with getting drivers to work with the integrated motherboard. that came in the Vista Computer.
So if you go the XP pro route I'd either buy it that way or build it from the ground up using XP compatible hardware.
Just my 2c.
If it works.....Don't fix it!