[tagawa]

From the user login screen, select the classic desktop from the bar at the bottom. This works well on my machine with roughly the same spec.

EDIT: Come to think of it, I think I heard they'd removed this in Ubuntu 11.10. It's there on 11.04, at least.

[ImprovedSilence]

It's in 11.10 too, it's the gear right in the login box, as opposed to the bottom of the screen.

edit: I've become a fan of KDE recently, and I've been able to get it looking and working the best, so that's what it is for now.