Contains the icons in all sizes,
Windows, Mac and PNG formats
The icons are free for personal use. Commercial use is not allowed.
Click Start → Control Panel → Appearance and Themes → Change the desktop background → Customize Desktop.
Select the icon and click the "Change icon" button.
Windows Vista / Windows 7
Click Start → Control Panel → Appearance and Personalization → Personalization or right click on your desktop and select Personalize → Change desktop icons → Change icon.
Select the icon, click Apply and OK.
Mac OS X
Are you in geeky mood? Use our Guide to change Dock icons in Mac OS X Leopard.