The XP - Vista discussion is a kind of outdated these days.
I'm using 2 laptops using Vista Business, even old Win95
and Win98 software run without any problems.
You can chose to run exefiles in wich mode you like by right-
click / properties.
Missing drivers might be a problem if connect old hardware,
but when buy new PC, internal hardwarecompability should be
just fine as is.
Why buy a Tyros3 and downgrade OS/software to Tyros2 or 1?

Cheers
GJ