Folder with Question Mark at Bootup.

I say reinstall. If that doesn't work then you might have a bad HDD on your hands.

 

Usually a file catalog/system error -- or someone moved/deleted a startup file when cleaning up the drive.

If you didn't move/delete a file, there is an error in the file system that'll need to be repaired.

Might have to boot in target mode and use another machine to fix the drive and recover the files. And may need 3rd party drive repair/recovery software.

If you don't fix the drive, you are just installing on top of a shaky file system.

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Though if you haven't been getting a lot of kernel panics lately and haven't been shutting the machine down with the power button instead of the menu -- you might be looking at a dying drive, or a dead one.

 

When my iMac did this, it was just after a power failure.

No matter what we tried, it would not boot properly.

If you have an external HDD you could do what I did ...
( prior to taking it to Apple )

I hooked up the external .... did a fresh install of OSX to the external ... booted off the external and accessed the internal HDD.

Was able to get almost all of my data off that drive before taking it to Apple.

Once this was done I attempted to reinstall the OS to the internal drive, it failed so I more or less confirmed it to be the HDD.

I took it to the Apple Store, they confirmed a dead HDD.


When I picked it up they informed me that they replaced the HDD and also LCD display pane as they saw a slight discoloration in one quarter.