Keyboard problems

Hi,

I bought my iMac (running on OS X Mountain Lion (10.8.2)) about a month ago now.

Unfortunately I have one persisting problem. The keys on my keyboard (volume control, play/pause etc..) do not work. They are the usual F-keys which have to be assigned.

However, I would really like to have the pre-sets working.

I've gone over the keyboard settings a million times and unlike previous versions I don't have the F1, F2 setting.

Can anyone help? Maybe suggest a drive I can install.

The keyboard is a the Apple Wireless Keyboard (http://www.apple.com/keyboard/)

Thanks in advance,

J