Paul Thurrott posted a quick guide about slipstream Office 2007 with SP2

While Microsoft made big promises for Windows Vista slipstreaming (and then failed mightily), it really came through with Office 2007: All you need to do is extract the updates from the service pack and then copy them to the Updates folder in the Office install folder structure. (And then optionally burn it to disc, though I just keep it up on a network share.) And because Office service packs are cumulative, you only need the latest service pack.

Slipstream Office 2007 with SP2