A flashing question mark in a folder

Rach, the folder with the question mark means the computer cannot find the startup system. This could happens because files that are needed to boot the computer are damaged, or the drive's directory is damaged. This can also happen when your computer has a dead drive.Try rebooting your computer while holding the Command R key. This will attempt to restart the computer using the Recovery partition. If it works, you'll know that your drive isn't dead. Use Disk Utility to repair the main partition. If it then download and install the operating system. If you can't reboot with the Command R key try using Command Option R which is an Internet recovery. If the drive's partition table were damaged but the drive itself is okay, you'll be able to use the Disk Utility program to create a new parition, install the OS, and then restore from your Backup. You can find plenty of information about this on here and here as well

"FIX

I had this problem upwards of 7 or 8 times, and I fixed it by replacing the defective cable. The more times I did this, the shorter the fix held for. I have now found a workaround by using a hard drive caddy. They are available of amazon for less than £10. You remove the optical drive (for CD/DVDs) and put the caddy in its place. The hard drive is then connected to the computer via different route, bypassing the defective data cable. It does mean you no longer have an optical drive, but that's a small price to pay to have a functional computer!

Caddy: https://www.amazon.co.uk/s/ref=nb_sb_nos..."

"I had the same problem. And after trying almost everything I finally find the solution, very simple by the way.

By turning off the computer and removing one of the memory ram card, turn on again and it will go straight like nothing, do your settings and turn off again and add again the removed ram.

Good luck"

Literally replace the hard drive cable. Take off the back the MacBook, remove the HDD, remove the cable from the logic board and any screw that are holding it down. Check serial number on it. Order one from amazon, prime it so you get it the day after and just put it back together the same way it came out.

the hard drive is new when I try to install the o s via external disc drive it wont load .Im probably doing something wrong........... I need help!!

in the case when checking the drive by using or booting from a recovery partition, or using the disk utility dont fix the problem, then it can be that the HDD is not properly connected, so check the data cables and make sure the HDD is properly installed. If you have done all this before and the problem continues, it could be that you have a dead drive, and you have to replace it!