Win XP
Apologies if I've drifted off subject here....
In my experience Win XP is a stable OS... I was a late to adopt - stuck with W2000 until XP had been around for a couple of years.. probably never move to Vista.
Despite my concerns with M$, I won't go down the Apple route: I have some of the same dislikes of their business practices as I do of M$.
I am serously looking at Ubuntu: every release seems to be impoving - I have IT professional friends who are very positive about how well Ubuntu is working for them.
(I'm not for or against any one OS - make your own choice)
If you still want a decent spec PC in the UK with XP installed, e-buyer are still offering some reasonable deals (look in the business PC section)
Regards
Martin.