Hi there and welcome
What error did you get when it failed? Do you still recall?
Can you power off the computer then hold the LEFT shift button down. With it held down, turn on the computer and keep tapping F8 until you get to a menu.
Choose Troubleshoot, then choose Advance
Then click on System Restore and perform a restore from the last restore point listed.
Let this complete and tell me if it then starts please.
what is the make and model of the computer?
ok, power it off
hold 0 (zero) and with it held down, turn on the computer and keep 0 held down until you get to the menu to choose
Troubleshoot, then choose Advance
Can you get to it this way?