Resolution Problem

[Billy]

My computer seems to be unable to display the 800x600
resolution properly. When I choose to apply the 800x600
setting in games (or elsewhere), basically, the
interface/screen is extended beyond the edges of the
monitor (so that the left and right sides of the screen
are essentially cropped off). I can display any other
resolution without this happening.

I regularly feel that this 800x600 is ideal for most of
my games, because anything lower looks a tad blocky,
whereas anything higher causes lag. However, the
incompatibilty of the resolution is a bit of an issue.

Can anyone identify the problem, or where it lies, and
if/how I could remedy it?