The question mark means your Book can't find a operating system. This is either a failed hard drive or corrupted system. Start up from your system installation DVD by inserting the disk and restarting holding down the "C" key. Go to the second screen pull down menu to Utilities, Disk Utility and see if you can repair the drive. If it won't repair, come back and give us the last three letters of your serial number so we can direct you to the correct hard drive installation procedure.