If you are having video problems such as not being able to fit the complete image on your screen this is due to your video card not supporting all the resolutions needed for many of the emulators. A number of these resolutions are not usually implemented by any Windows or DOS programs but needed for emulators since they emulate the resolutions of the old arcade machines or television screens. There are a few things you can do to resolve this:

1) The most useful tool is Scitech Display Doctor which you can get from here: http://www.scitechsoft.com It will allow you to display resolutions your video card does not naturally display such as EG 400x300. It will also upgrade your display to Vesa two or a Vesa 3, which are display modes that can produce an image quality and speedadvantage.

2) Many emulators support Mode-x graphics. This will also allow you to display unnatural resolutions which you video card could not normally cope with.

3) If you are having problems with your monitor of going into sleep mode this is usually due to the fact that your emulator is attempting to a display a resolution which is supported by your graphics card but not by your monitor. There is nothing much you can do about this except again attempting to use the Mode-x resolutions, playing with the scanlines option or simply attempting to play in another resolution.