Show 12 Hour & AM / PM Symbols in System Tray Clock in Windows 7

1.Click On Start Menu and Click Control Panel

2.Click  On 'Region and Language'

3.Click on 'Additional settings'

4.Click on 'Time' Tab

5.Change the value of  "Long time"  to "hh:mm:ss tt"

6.Change the "Short time" to "h:mm tt"

7.Click On OK Button... And Enjoy....