Visit an iTunes visualization plug-in website like Plug-Ins World, Volcano Kit and Sound Spectrum.
Click the “Download” link for the plug-in you would like to use. Click “Save” to save the plug-in to your computer's hard drive.
Click the Windows "Start” menu button. Select “Computer."
Navigate to the downloaded plug-in folder on your hard drive. Right-click the folder. Select “Copy.”
Navigate to the “Users” folder in your hard drive's root directory. Double-click your username.
Open the "Appdata" folder. Navigate to "Roaming," "Apple Computer," "iTunes" and "iTunes Plug-ins."
Right-click anywhere in the blank space inside the iTunes Plug-ins folder. Select “Paste” to add the new visualization to iTunes.