There are some icons which aren’t classed as notifications, you may want to remove from the Windows 7 task bar.
Items like the clock, volume, network, and power icons are all classed as system icons, and not part of the normal “Desktop Notifications” settings (where you would find icons for Live Messenger, Outlook, etc).
If you do want to add or remove certain system tray notification icons, you can do this by:
Control Panel -> Notification Area Icons -> Turn system icons on or off (at the bottom of the window, in blue text)
You’ll then be able to modify what gets shown there on the taskbar.