what are specs of PC? What motherboard have you got (if its a brand name pc, what make/model?)
if you start PC and restart it just as you get to the spinning dots, and repeat that process 3 or so times it should load you into automatic repair. This might fix it or offer more options.
choose advanced, this loads windows recovery environment (Or should)
try to get into safe mode and look at device manager for errors or unknown devices
choose troubleshoot
choose advanced
choose start up options
hit the restart button
choose a safe mode (it doesn't matter which) by using number associated with it.
PC will restart and load safe mode
you could also try start up repair with same trick
get to win re
choose troubleshoot
choose advanced...