This sounds as though you are not using the screen's native resolution. LCDs are basically designed to work with one particular screen resolution. You should check that you are using the correct resolution for the screen.
If you have changed from a CRT to an LCD you will probably find that you need to increase the resolution that you use.
(Note to people about to buy an LCD screen. Check that your PC's graphics card can display the resolution that the LCD is designed to display before you buy one, otherwise you may find that you need to upgrade your graphics card.)
TS
June 2005