You spent on the Ultimate version there I see. They were sold out at one pc fair atttended. Have fun getting drivers! 2gb has been running here well for the average gaming with Prey, Fear, Half Life 2, and others. Vista no longer has the 4gb max that XP saw. Having 2gb will help with the load of additional items that load with Windows like the new welcome center and side bar.
Plan on spending far more time installing games and other programs with all of the new security prompts seen. Even with the firewall turned off and the full version of the Windows Defender disabled those still act like a second firewall is running where you need to give administrative permission on everything.