Windows 10 wont boot at all!

[ByMega]

So yes, my power went out last night & had it on back again later the next day. I turned my computer back on & was just casually playing LoL. I went to go take a shower & when I came back my computers screen was black with a blinking underscore. At first I did not know what to do. I can go to the BIOS but clicking F12. I checked on the Dell Diagnostics tool in the BIOS & tells me everything is ok. At first I thought it was my HDD but its telling me its all ok. I dont know what to do. I already ran Hirens to see if anything was wrong with the HDD & its all fine. My only hope is that I would need to reinstall the OS. Please help!

PC Specs:
Dell Optiplex 3020 Micro Form Factor
Intel Core i5 4590 3.30GHz
Toshiba 1TB HDD
Radeon R7 250 2GB DDR3
16GB RAM DDR3

 

[Colif]

On another PC, download the Windows 10 media creation tool and use it to make a win 10 installer on USB

change boot order so USB is first, hdd second
boot from installer
on screen after languages, choose repair this pc, not install.
choose troubleshoot
choose advanced
choose start up repair - this will scan PC and maybe fix this - will ask for logon info

can also try safe mode
follow above steps but instead of start up repair, choose start up options
choose a safe mode (there are 3)
pc will restart in safe mode - you don't have to do anything, sometimes just booting into safe mode fixes this. restart pc and see if it boots

See how they go