[ubuntu-uk] Visual Effects are greyed out

[Gordon Burgess-Parker]

I installed 10.04 Remix on my Laptop from a flash drive (because it's
MUCH faster than using the CD) but if I right-click on the desktop,
choose "Change Desktop background" and click on the Visual Effects tab,
it's set to None and all the options are greyed out.
I know that the graphics card is good because it runs Aero on (cough
cough!) Windows 7....
How do I enable this?