To go full screen in Windows, simply:
rem Go to SETUP.AGC and set FULLSCREEN=1
SetVirtualResolution ( GetDeviceWidth(), GetDeviceHeight() )
LoadImage(1,"background1.jpg")
CreateSprite(1,1)
while GetPointerPressed()=0
Sync()
endwhile
This will give you full screen to the size of the desktop, and a perfect 1:1 back buffer for your graphics. Be aware that when you do this your bitmap fonts will be substantially smaller than normal on large resolutions so you should look at the documentation on how you can provide higher resolution fonts for your app.