I wouldn't recommend switching motherboards on a Dell as they are proprietary (non standard) In any case stick with another Dell mobo or the plugs wont fit properly on a standard ATX/micro ATX form factor motherboard. The CPU is a socket 478, it supp...
try www.crucial.co.uk and let it scan your computer and see if they can match it, I hate DELL
buy a monitor or lcd tv (tv is same price or cheaper at circuit city) that lets you use both capabilities by choosing normal or stretched or wide screen format when you use the vga input from the computer