Sounds like your resolution is too high. On the display options, change your resolution (settings tab) to 800 x 600 or 1024 x 768.
If you're using a CRT monitor, go on the advanced button and look in monitor and adaptor (look in both) and change the refresh rate. Try 75Hz. This should make the monitor easier on the eyes.
You might need to use the controls on your monitor to fine tune horizontal and vertical size/positon etc after adjusting settings.