Basically, as far as I know, you can't autohide it.
You can set it so that it is not always on top of other windows (The Windows-Spacebar key combination will bring it to the foreground if it is hidden behind other windows). But, again, as far as I know, there is no auto-hide feature built into the sidebar in Vista.
Desktop Sidebar is a different story as I believe they have an auto-hide feature..
Ep, glad to see you come back and tidy up...did want to ask a one day favor, I want to enhance my resume , was hoping you could make me administrator for a day, if so, take me right off since I won't be here to do anything, and don't know the slightest about the board, but it would be nice putting "served administrator osnn", if can do, THANKS