Do you have important information on this laptop?
The reason I ask is because sometimes this behavior is an indication of an impending hard-drive failure and attempting to rectify the situation could lead to complete failure of the drive and loss of data.
Okay, in that case, I recommend you have a service person look at the system in person, because I don't want to walk you through doing a hard drive diagnostic and have the drive fail completely. If you need data recovery services you can remove the drive from the computer and send it to a company called Gillware who can recover just about anything short of a completely destroyed hard drive. You can get more information about them and their services here: http://gillware.com/?affiliate=23854
I realize this probably wasn't the answer you were hoping for, but if you find the information useful, please consider giving me a positive rating. If you are not satisfied, please do not rate negatively, you can request a refund by sending an e-mail to***@******.***