harde reset samsung galaxy s2 gt-i9100

-Warning! Do this at your own risk! All your phone data (contacts,photos,videos,music,messages,a­plications,games,files,) will be lost! Please make backup first if you can
.If you forgot your screen lock combination follow these steps

Power off your phone * 
Press together volume up + home button + power button * 
Release your fingers of the phone when Samsung logo appear * 
Choose with volume buttons "wipe data/factory reset" and select it with power button * 
Choose "yes" with volume buttons and select it with power button * 
Wait untiil format is complete * 
Select "reboot" *