Computer Gyan

1 - Go to Run (Press Window key + R) 2- Then Type gpedit.msc 3- Then Press Enter Then It will Display Group Policy Dialog Box Like below .. 4- Then Double Click On Administrative Templates 5- Then Double Click On Control panel 6- Then Click On Personalization 7- Then In Right Side Of  Dialog Box Double Click on Prevent Changing  Desktop Background 8 - Then It will Display Prevent Changing Desktop Background Dialog Box 9- Then Click On Enable Option 10- Then Click On Apply Then Click On OK .

Press Ctrl + Shift + Esc From Keyboard Then It will Display your Task Manager Dialog Box Like Below Image

            Click on Date & Time on Taskbar       Then click on Change date & Time settings Then Click On  Change Date & Tim e Then Click On Calendar Settings                    Then Select Time Tab           Then Edit AM & PM symbol Then Click On Apply Then Click On OK The Output is  

1st step -Go to Run             Then Type                            netplwiz in Run Dialog Box Then Click on Advanced Tab Then Mark the chekbox require users to press Ctrl+Alt+Del Then Click On Apply...Then Click on  OK button.