Unlocking code for the phone

Question

i have set lock pin code for my PDA(frst time set)..when i off the phone n on back,the screen is only appear windows mobile and icons at the top side(battery,coverage n so on) but icon 4 menu start is not appeared..it continues like that even i try to off the fon..i can receive the calls n answer it..but i cant read the msg even the sound of receiving msg formed..what should i do?