Do graphics and text appear grainy or chunky? Does it look as though application windows no longer fit on screen in the way you're used to? A resolution or device mix-up can wreak this kind of havoc. If you can read the screen well enough, review the graphics resolution and other settings by right-clicking the Windows desktop, clicking Properties, and selecting the Settings tab. Check the Screen Resolution slider bar and the graphics card model to confirm that they are as expected. When this kind of problem occurs in a game, driver software could be at fault. Go to the vendor's Web site for the most recent driver. Sometimes, an older, more stable driver may produce better results than the latest version.You might also check for a patch to the game.

If the screen has become extremely dim or has acquired a red or blue cast, a loose or damaged cable may be allowing only a portion of the intended signal through. Also check the pins in the VGA cable plug to see if they are bent--you can use a pair of needle-nose pliers to gently straighten pins before reconnecting the cable. If you have a CRT monitor and the image appears wavy, a likelier culprit is a magnetic field emanating from a speaker, clock, or second monitor and scrambling your CRT. Try moving any electric devices farther from the display.

Do you have a CRT monitor that periodically loses focus or makes popping noises? Or has your LCD screen grown very dim or begun flickering annoyingly? If twiddling with controls and (in the case of CRTs) manually degaussing the display does not work, there's a good chance your monitor is preparing to shuffle off this mortal coil. Take it in for service or replace it.