I originally installed Ubuntu then changed to Lubuntu because I have a 1 ghz CPU and .5 gigs of RAM.
Lubuntu detects my HD monitor to be 16:10, and it cuts of a little bit of the screen (half the scroll bar). I need 16:9 resolution.
Lubuntu Menu (bottom left corner of the screen) -> Preferences -> Monitor Settings -> Resolution
Set it to your screen resolution (e.g. 1280x720, not 16:9), then click on Apply.