How to change language?

[Henrik Nilsen Omma]

I installed Ubuntu on my spare laptop from the sounder 9 CD about 2 
weeks ago. I've updated things gradually, and AFAICT I now have an up to 
date final Warty System, running nicely. I'd like to pass the machine on 
to my mother now, as hers has died. Although her English is fairly good, 
I'm sure she'd prefer it to be in Norwegian. Changing the keyboard 
layout is easy, but how do I change the default language of menus, etc. 
in Gnome, post-install? I'd think it would be obvious, but I can't seem 
to find it ...

Thanks,
    Henrik