Hey there!
Sorry to hear your having troubles with your Mac. First and foremost, have a little read of the following article by Apple:
https://support.apple.com/en-gb/HT204323
I presume the grey folder icon contains a flashing question mark at startup. If this is the case, then it means your Mac can't find its system software or a bootable disk. That can either mean it can't find the hard drive or the Operating System data on the hard drive is somehow corrupted.
May I ask what operation system you are running? You may want to use the installation DVD or USB installer to insert and reboot. As soon as you hear the boot chime, hold down the "c" key on your keyboard (or the Option Key until the Install Disk shows up) until the apple shows up. That will force your MacBook to boot from the install DVD in the optical drive. From there you can repair disk or set up new partition and clean install if necessary (last resort).
Or you may want to try boot from the recovery partition (Command +R on boot) and use Disk Utility to repair your partition, depending on which software version you are running.