Win7 screen resolution not changing

I have a Dell desktop and I just upgraded it to Windows 7 Ultimate from XP Pro. Ever since then, my resolution is stick at, like, 640x280 and everything is HUGE! I can barely do anything!!!!I am a pretty good tech guy, but here, I'm lost. When I try to change it In Control Panel, the whole thing is Grayed out. All is says is a yellow ! with a message that says "if your resolution is below 1280x800, then some items might not fit in the screen" which is soo true. PLEASE HELP!!!!
P.s. I am running 32-bit, if that helps