at the risk of getting myself scraped over the coals here im going to offer my 0.02c..
i have been through this whole Vista/XP fight about many of my cad programs already, on many different forums..
to me the answer is simple..
Mill = US$9750
CAM = US$2999
Mach = US$199
Profit per job = US$100 (in my case)
Controller PC + XP = US$150
no brainer.. everything works with XP.. why mess with it.. if it wont work with your laptop.. buy a refurbed dell unit off ebay for $150 preloaded with xp and have done with it..
this equipment earns you money, its is dedicated , it does only one job, and as such should have a dedicated pc that belongs to it? if it likes XP give it XP..
just my opinion guys