Usually he's off on my machine. I clicked on him said "turn you off" & got nothing useful. Then I entered "turn assistant off" & found this.

The Office Assistant is distracting. Choose a different Office Assistant [not good enough, stuff deleted]

Limit its movements [also not enough]

Move the Assistant [are you kidding? It's always on top of a button I want to click]

Here's the real help
Hide the Assistant On the Help menu, click Hide the Office Assistant.

Turn off the Assistant Click the Assistant, and then click Options. On the Options tab, clear the Use the Office Assistant check box.