its probably a display settings. You can try a Few things.
1. Click on Start
1. Choose Control Panel
2. Click on System Icon
3. Choose the "Advanced" tab, click "Settings" under "Performance"
4. Under the "Visual Effects" tab I Chose (checked) Use Drop Shadows for Icon Labels
For Vista and UP
1. Click Start, and then click Control Panel.
2. Click Performance and Maintenance, and then click System.
3. On the Advanced tab, click Settings under Performance.
4. Click to clear the Use drop shadows for icon labels on the desktop check box, click Apply, and then click OK two times.
5. Close Control Panel
You may also have an Active Back ground. For XP Only
1. Right click on desktop then properties
2. Click on "desktop" tab on the top then click on "customize desktop" button at the bottom
3. click on "Web" tab on the top then uncheck the check box "Lock desktop items" then click "ok"