I bought this Macbook Pro A1278 used last November and it worked great. About 2 weeks ago the hard drive was making a clicking noise but still worked fine. 2 days later when I booted up the MBP it would only boot to the folder with question mark. I took the hard drive out to find that it was dead. I purchased a new 500GB hard drive, installed it and can't get it to boot from the 10.6.4 disc that I received with the macbook. I also tried resetting PRAM and nothing! I also tried booting holdind down the option key and it boots to a grey screen with a lock. I contacted the seller I purchased from and of course 11 months later they said they know nothing about another password. Can someone PLEASE HELP, I paid over $1000 for this laptop about 11 months ago.