Here's the program. The size is 223 kilobytes, takes up about 2000 kilobytes to run, so not much.
It does not hide the start button, but that shouldn't be a problem.
If you decide to use this without autohide, it will show the desktop below the area where the taskbar was. If you do use autohide, you'll get the full screen, but you won't see the taskbar if you mouse down there until you hit the hotkey.
Hope that's not a problem.