Try holding down one of these button combinations: 
  
On some phones, some of these combinations may power the phone on into the 
		
Bootloader or 
		
Download Mode screen. When a list of options appears, use the 
VOLUME buttons to navigate the list, and then press 
POWER to select an option. 
		
Note: Make sure you do not select the other options on the screen. Doing so may void your warranty or brick your phone.