*shrugs* I've been administering Windows servers for many years, and I have never had a server crash that cannot be traced to third party code. And I never see the need to reboot them every week or whatever either. Much that is said about windows is said by those that have little experience of it, like many things really, TVR's for example.
However, I would still rather run a "leaner" OS than a minimum standard Windows (or a minimum standard Linux) install for a car PC, if one is available.
So build yourself a custom minimal install of XP then. Quite a lot of bumf you can actually strip out of a custom installer.
Take a look at nLite.