Here's how you can customize your user account icon.
Single-click the start menu and choose Control Panel.
Single-click the User Accounts icon.
Find the user account you'd like to change the icon for and click on it.
Click the text that says "Change My Picture."
You'll have the option to either pick one of the predefined icons or choose your own.
If you like one of the predefined icons, just highlight the one you like and click the button labeled "Change Picture."
If you'd like to use your own picture, just click the magnifying glass or the text labeled "Browse for more pictures." This will launch a dialog box directing you to navigate to where your new picture is stored. After you find it, just click Open to save your new changes.