I personally like WinXP, certainly my favourite of the Windows operating systems, and I pretty much think they 'cracked it' with XP Professional (however I still like Madriva because it's different

)
Bloodline has a good point about the Microsoft business models. Vista is not a good option now, but may be in 2 or so years time once the teething problems have been ironed out.
My recipe for stable computer and internet life at very low cost, or no cost

:
Windows XP
Spybot
Ad-Aware
AVG Free
Oh, and hello :-D