Change usergroup for newly registered users
Currently when someone registers with our site they are given 10MB of disk space for uploading their photos and are classified as a Registered user. I want to run a temporary promotion that will give new users who register with our site 30MB of disk space.
I've set up a new usergroup called Promo. What I need to know is where in the code can I change it so that a new user is automatically registered as a Promo user instead of a Registered user. Then, when my promotion ends, I can revert back to making new users part of the Registered usergroup.