The shadows used for Windows 7 desktop icons can be pretty nasty. Especially with a white background, the text under the icons can become unclear.
You can disable the shadows by opening your System Properties / Performance options / Visual Effects and uncheck the option “Use drop shadows for icon labels on the desktop”.
If you want to push this setting for your clients, you can use the registry setting below. Copy the text into notepad and save it as <filename>.reg. Import the setting by a logon script or through group policy preferences (Windows Server 2008) under the User Configuration.
Windows Registry Editor Version 5.00