I've Office XP, with only Word & Excel installed. Whenever it offers to install unrelated updates of PowerPoint, Outlook, Access & Publisher I just go ahead & do it. It sometimes also offers Office 2007 (remember my version is Office XP) updates that I also install. I've not had a single problem because of this.
In other words, the 'unrelated' updates are perfectly safe to install, & there must be a good reason (unknown to the rest of us of course) for Windows/Microsoft Office Updates offering them. G