Trimmed version of windows what? I beleive if you do a search on tiny XP there are links to copies of reduced footprint XP that you can use but obviously you'll need your XP licence for them. They should come with instructions (generally burn the image to a CD and then bood the netbook from that).
That said, I've just got a dell netbook for my wife with bog standard XP installed on it and it's absolutely fine. I was hoping for Windows 7 as my experience with that it that it is as good as XP but with some better laptop features.
Avoid vista, it's worse than a certain dealership in Battersea was (is?)