If you want to add one of the Menu Extras (Clock, CPU, Displays, Spaces, etc.) to your menu bar, or if you’ve accidentally removed one that you need, here’s how to easily place them on the menu bar.
1. Open Finder.
2. In the left pane, select Macintosh HD under Devices.
3. In the right pane, browse to System, then Library, CoreServices, and open Menu Extras.
4. A list of files with a .menu extension will be displayed. Double-clicking the desired Menu Extra will install activate it on the Menu Bar. Choices are: AirPort, Battery, Bluetooth, Clock, CPU, Displays, Eject, Fax, HomeSync, iChat, Ink, IrDA, PCCard, PPP, PPPoE, RemoteDesktop, Script Menu, Spaces, Sync, TextInput, TimeMachine, Universal Access, User, Verizon, Volume, VPN, and WWAN.
If you wish to remove any of the Menu Extras from the Menu Bar, simply hold down the Command key and click+drag the icon off of the Menu Bar.