Darkwater409

I downloaded this on my desktop and accidentally messed up a setting. Now I can't log into my computer. I'm literally having to borrow my step grandfather's laptop for the month before i am officially screwed. I can't afford a new computer and sadly mine has no backup disc and didnt come with an os disc. Can someone please help me figure out how to undo it. The computer I have it on is a Gateway SX series with Windows 8.1 on it. Ever since I made that mistake it causes my computer screen to flash on and off 3 times and then sends me straight back to the login screen. It doesn't give me enough time to clear the setting before it is back on the login screen. Also, my computer is set to quick start which sadly disables the root boot menu. Can someone please help me? I really need this problem fixed. I can't afford a new os disc and I definitely can't afford a new computer. I seriously need to get this problem fixed and fast. Sincerely, Darkwater409