[iPhone] Syncing with iTunes

How do I make a new computer sync with my iphone.

This is the third computer I've used with the phone, and while it will do my music and photos, how do I get the apps and shit I've downloaded backed up ON the new computer? It seems to only want to do it with the first computer I ever plugged it into.

Google for 'syncing iPhone multiple computers' I can't remember exactly how it's
done, but it was something like duplicating an ID string on the new computer.

Ok thanks I'll look into that... this will be the only computer from now on I'll be syncing anyways.