To make this clear: With &pgr;, technically, you still only have one screen. Neither PM nor your video driver know anything about virtual desktops. All &pgr; does when switching desktops is to move windows off and onto your one visible screen. That is, if you switch one desktop to the right, &pgr; moves all windows to the left by the size of your physical screen (which makes them invisible, of course). As a result, no special hardware or software or drivers are required. If your computer can handle moving windows, it can use &pgr;.

The small &pgr; pager window then does a number of calculations to make all windows look as if they were part of a huge virtual screen, but your physical screen really doesn't change -- it's the windows that are moved.

&pgr; also needs the &xwp; PM hook to be able to track window movement -- for one, to reflect window changes in the &pgr; window, secondly to be informed when windows are created or destroyed for any reason. It can then, for example, automatically switch desktops (that is, move all windows) if the focus is given to a window of another desktop.