I have ordered an external hard drive so I can backup my work, and install XP + Linux. I will post the new 3D Mark scores for XP; so you can see if Vista or XP makes any difference to performance.
I can say after using Vista for over a month, I wish I had gone for XP.
Vista is very unstable.. It crashes at least once a day.
It appears that Microsoft allows you to downgrade your copy of Vista if it is Vista Business or Ultimate. However I can find out how your supposed to achieve this.