peter@peter-desktop:~$ compiz --replace
Checking for Xgl: not present.
xset q doesn't reveal the location of the log file. Using fallback /var/log/Xorg.0.log
Detected PCI ID for VGA: Flags: bus master, VGA palette snoop, 66MHz, medium devsel, latency 64
Checking for texture_from_pixmap: present.
Checking for non power of two support: present.
Checking for Composite extension: present.
Checking screen 1Comparing resolution (1920x1200) to maximum 3D texture size (8192): Passed.
Checking for Software Rasterizer: Not present.
Checking for nVidia: present.
Checking for FBConfig: present.
running under gnome seesion, checking for gnomecompat
Checking for Xgl: not present.
/usr/bin/compiz.real (core) - Error: Could not acquire compositing manager selection on screen 0 display ":0.0"
/usr/bin/compiz.real (core) - Fatal: No manageable screens found on display :0.0