Before doing anything else, it might be best to check your monitor first.
Use this test card:
http://www.reeddesign.co.uk/testcard.htm
If you can't read all of the numbers, from 0 through to 10, on both of the numbered lines, you need to adjust your monitor settings.
If you can't get the display to show all of the numbers by adjusting the brightness and contrast of your monitor, you might be able to tweak the settings of your graphics card to fix the problem. (That's usually possible if you've got a separate graphics card but sometimes impossible if you've only got 'onboard graphics' on your motherboard).
If you can't get the display to show 0 to 10 on both lines, it's probably time to change your monitor.
Chris