SWks 2009 Runs Best on Windows ?

We have XP Pro 32, 64 & Vista for SolidWorks 2009 which is now arguably half a year into its lifespan.

For those who have experimented:

1. Which Windows version gives the most reliable uptime?
2. Which Windows version runs fastest?

This assumes you keep the system from malware and various crap applications and corruption, which I do scrupulously. My SolidWorks install goes on a machine that never sees the light of a network or internet (after initial OS updates), and hence it runs SWks 2006 without any externally created problems.

There are things 2006 does not do and a few which cause SWks to quit, so it is time to prepare to 'move up'.

Many Thanks - Bo