*ACTUALLY USEFUL NOTE, THIS IS NEW FOR ME*
I do Direct3D programming, and I know that to use Set Window On, your computer must be able to create a D3DDevice in Windowed mode. First, try changing your desktop screen res before starting the program (make it something low, USE 16 BIT OR 32 BIT ONLY)
Hell, one of my computers couldn't create a D3DDevice at 640x480x16. It could do 800x600x32, but not 640x48x16 (note: the mentioned computer is currently busy marinating with the flies in the tip

)
* USE A DIFFERENT COMPUTER *
and fix your DarkBasic, per JessTicular's suggestion.
Whatever.
[img src=http://blanky.pt-web.net/ddd.gif] >::p