I tend to point specific OS versions at computers of a specific size, on an old box, run win2000, its stable, reliable and still does most things OK. If the box is not all that old, run XP SP3 as its very robust and still runs most 32 bit software. It will work with under 1 gig of memory but works a lot better with 4 gig. 2 gig is a good compromise.
If you have a late i7 with 8 gig or more and you don't mind the cheezy glass interface, run Win7 64 bit, it will run the newer 64 bit apps and can run most of the older 32 bit apps, even if you have to run them in XP mode. I would not recomment XP 64 as it was an orphan, if you want 64 bit operations, use Win7 64.
xandaz,
Is that your youngster in your logo ?