Clean the screen
To keep it as pristine as possible, you can
A) get one of the kits from best buy or circuit city for cleaning the big screen TV's - perhaps comp usa has a similar set for monitors..
B) use as cloth designed to clean camera lenses, dampen part of it slightly, fold it over let the dry part absord some of the moisture, and wipe away.
p.s. - I probably shouldn't say this.... but I know someone who uses lense cleaner for his glasses (plastic lenses), but you must be careful with which type of that you choose - buyer beware.
as for 4:3 images... if it's your desk top you are asking about, system prefs-> desktop screen saver -> desktop -> select stretch to fill screen or fill screen.
hope that helps? if not please be a little more specific on what your trying to do.
-Munch