I'm building a clean VM of Ubuntu 7.10 "Gutsy Gibbon" and thought I'd remove the fancy Compiz window manager. I then discovered the previous version was running one called MetaCity and looked into reenabling that. Uninstalling Compiz isn't enough - you have to do the following to enable MetaCity, otherwise you get some weird effects.
So, from http://ohioloco.ubuntuforums.org/showthread.php?p=3770282 :
As root (sudo gedit), modify: /usr/share/gnome/default.session and change
0,RestartCommand=gnome-wm --sm-client-id default0
TO:
0,RestartCommand=gnome-wm --default-wm /usr/bin/metacity --sm-client-id default0
