Which phone do you have, which firmware version, which PC, and what have you done to the phone to make you ask this question?
It's very difficult to brick an iPhone unless you physically damage it, like dropping it in the toilet or running over it with your car.
Erm... I mean failbreak (Failed Jailbreak)... My friend i think failed his jailbreak, and his screen stays on the apple logo
soz ive been away from the comp cause my internet was down. I meant, my friend said that it stayed at the apple logo. Is that bricked?