My system not shutdown i

Question

my system not shutdown i have to press down the power button,but yes
when i start my system it shows one sceen in the code something "]]["
then only OK button,i press the ok then the user screen comes but not
able to write down the password so i again have to poweroff and agIN
RESTART THEN SOMETIMES the screen not appears and i can wrtie down thje
password and starts the PC. Please reply as soon as possible..i facing
this problem long time....thanks in advance...