Toshiba Factory Reset/Defaults

I have a Toshiba Satellite computer (model number C855D-S5354).
For a long time now, i have been trying to reset the computer back to it's original setting's, but with no luck.
I have tried going to "PC Setting's", selecting "General", and then selecting both choices offered, i.e keep my files and reset or fully clean the drive. I have had no success.
I was reading yesterday that if you turn off your computer, then hold down the "Zero" key, and then press the "power button" until you hear a beep, and then let go off the "Zero" button, that this will bring up "hidden" alternatives. I did this, and selected "reset pc", but in all the thing's i have tried, a message informs me that there was a problem resetting the pc, and no changes have been made. No changes had been made.
I scanned the computer with more than one anti-virus program, and the computer is clean.

I f anyone can help with this issue, i would be grateful.
A full step-by-step guide to show me what i have to do would be also great, as following the instructions, (including altering any registry items that may be needed), should be no problem.

Finally, my own opinion is that something has gone terribly wrong, and that having to purchase a Recovery CD or the original Installation disc from Toshiba, may be my alternative.
Thank you.