How to change default language from English (US) to (UK)? 10pts asap?

It is by default on (US), I need it on (UK).



I change it temporarily using the small icon that says 'EN' on the task bar at the bottom, (Vista)



How do I make it so when I log on, it is ENG(UK)?



Thanks in advanced, working answer gets 10points asap.How to change default language from English (US) to (UK)? 10pts asap?
here u go