CCleaner gives you an option to clear the System tray (Notification area) icons:
Link Removed due to 404 Error
But in my experience, on Windows 7, the CCleaner method of clearing the notification area is a bit hit or miss. The manual method of using a small registry hack and then stopping and starting Explorer however, works every time.
Copy and save this code as a .reg file.
Code:
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Classes\Local Settings\Software\Microsoft\Windows\CurrentVersion\TrayNotify]
"IconStream"=-
"PastIconsStream"=-
Open Task Manager
(R-click taskbar for a Start option) to the processes tab in preparation.
Now merge the .reg file you created into your registry.
Back to the Task...