A shutdown
B. Power
C. When the first boot animation disappears immediately press and hold the phone left soft key (that is usually the Menu key left the virtual key) and hold until the phone into the system
D. lower left corner of the screen when the phone will display "safe mode", before you install the software will be blocked, and then you can delete files
completely feasible, into safe mode, all software is not loaded, the program can not see at all, only in the set, the program in order to see, so we can delete useless software, or the software in question.