Right-click a blank spot on your desktop and click Properties.
Click the settings tab, and tell me what your screen resolution and color quality is set at.
Also, are you on XP? Finally, do you know what model your graphics card and monitor are? Your monitor should say on the front of it; the graphics card can be found by right-clicking My Computer on the desktop, clicking properties, then clicking the Hardware tab, following by the Device Manager button. Once this window opens, click the plus sign next to the "display adapters" item, and it should tell you what your graphics card is.