How do I switch on four finger trackpad gestures?

Hi,

I finally upgraded to Snow Leopard (clean install, then restored backup via migration assistant), and wanted to make use of the three and four finger gestures on the trackpad. However, in my system preferences - trackpad - there is no option for further gestures or similar.

My macbook is fairly old (mid-2007), is the trackpad not equipped for that?

Happy to ask this question in the Macbook section, too, but I first wanted to check if there's a software glitch.

Cheers

Veronika