question mark folder when i startup?

You must have a bad contact somewhere, most probable the ribbon or its contacts or the HDD itself. It will surely show up again sooner or later.

i have the same problems and everytime i try any solution nothing happens my sdceen stays white... resetting the pram i heard the chimes and it didnt do anything... plz help

I have a similar problem: My old hard drive crashed so I installed a new one. Now when I turn on the computer the question mark box comes up. I tried resetting the PRAM but that did not work and I have no idea what I'm doing. Any suggestions?

I all of the above after the screen of death without luck then just spotted your post and tried as a last resort. Machine in the process internet recovery. Whoop!

Okay, I had this problem happen to me last night. None of the solutions were working, not even the starting up <Command> + <Option> + <r>, which boots it up via the internet and lets you use Disk Utility, or re-install the system from the internet (Yosemite), or re-install everything from a Time Machine backup. So I turned it off overnight, to get ready to get my father to help me (he has a repair program that does a better job that Disk Utility). Then my sister late last night mentioned that she'd had that happen and had simply turned her computer off for a while. So this morning I turned my computer back on.

Wonder of wonders, it's working.

So I would advise that the first thing you do when you encounter this problem is turn your computer off for approximately half an hour to an hour, minimum. Then if that doesn't work, go on to try the other suggestions.

What should I do if I dun hv a start up disk

I tried everything. Nothing works. Tried recovering but some error !

Please help!