Skip down and do #9 immediately, do #3 and take the machine in for service or replace hard drive yourself if possible. Grinding, clicking or other never before heard strange sounds coming from your hard drive, always requires Disk Utility > repair, SMART status bad, it's likely failing, especially if it's more than 5 years old or has been subjected to shock. Stable/fast Internet is required, preferably a Ethernet cable to your router, or if the modem, powered off/on to reset it.
If you have a firmware password, that will have to be disabled first. Disconnect all other hardware from the problem Mac.
Mac utility to reset file permissions Pc#
Mac utility to reset file permissions software#
If it's too much for you, there are local PC/Mac software repair and data recovery services, for hardware repairs you should take it to a Apple Authorized Repair. It's designed for those who already have a good familiarity with how Mac's work, is almost all Apple support documented. If this User Tip appears to be quite involved, it's designed to very through and systematic process to achieve success.