Reset bios black screen when downloaded

Please help, you need to reset bios or sew bios. The problem of the next child climbed in the settings bios, then in the bios to enter is not possible - black screen, in the windows enters well on the look like win7 and everything hangs and lags … Please help, how to make a reset to factory settings, there was an attempt to roll back Windows, well the process hung

Hello,please contact