If you suspect that your disk is having trouble, make sure you back up your data files to another drive or to DVD-R as soon as possible. One symptom of a failing drive is long pauses to do anything. Another is any unusual clicking noises coming from the drive.
Check the SMART status of your hard drive to see if it may be a failing drive
Mac:
SMART status is displayed in the Disk Utility screen
Windows:
http://www.computerhope.com/jargon/s/smart.htm
http://www.ariolic.com/activesmart/hard-disk-smart-status.html
Disk testing utilities,
Mac: Disk Utility, in the Applications: Utilities folder
http://support.apple.com/kb/ht1782
Windows
Seagate Seatools http://www.seagate.com/www/en-us/support/downloads/seatools
Western Digital Lifeguard Tools http://support.wdc.com/product/download.asp?lang=en
Run a disk check:
Windows: Go to the Start menu and choose command prompt. This will take you to the DOS command prompt where you can use the chkdsk /f command to try to repair the hard drive. At the C:> prompt type CHKDSK /F {return}
Mac: Hold the Shift key down through startup to start in Safe Mode: http://support.apple.com/kb/HT1564 This will take much longer than a normal startup.
(Starting in Safe Mode will automatically run the fsck disk maintenance routine.)
If you have a problem with your hard drive, the first thing is to stop using it. If possible, boot your computer from a different drive. You can remove the problem hard drive from the machine, install a new one and install your OS, and then try recovering data from the problem drive and/or running drive and partition repair software. At this point you are not too concerned about saving your OS on that problem drive, but getting all your data (including your email files, which are often buried in your User folder). Once you have backed up your data you can work on repairing the data structure of the drive, assuming it has no physical breakdowns. Its easier backing up data from a drive if it is not also the boot drive of the machine.
Recovering files:
https://computer-answers.ca/2011/computer-questions/windows-questions/q-my-computer-is-broken-and-i-need-the-data/