PC Broken after Monitor Overclock

[Charlie_65]

I overclocked my 60hz monitor to 75 Hz and it worked fine. So I tried to go to 80hz and after restarting my pc the screen just flashed colours, white, red, green, blue. It does this a couple of times and then it says "not optimum mode, recommended mode 1920x1080 60hz" please someone help I had a lot of work on my pc I need back

 

[Kollosso]

What brand and model is your monitor? There is usually a way to reset it to factory defaults involving pressing certain Buttons in a certain way, but I need these informations to tell you how.