Ron,
The answer doesn't really have much to do with PowerPoint. Video output is
a function of the video card and most are set for a 4:3 ratio. Some video
cards allow for a 16:9 ratio if the right device drivers are installed.
WARNING: Do NOT switch it to a 16:9 ratio while hooked to a standard
monitor. The result will likely be a burned out monitor!
Austin Myers
MS PowerPoint MVP Team