On another pc, download this and make a Windows 10 Install USB or DVD:
Win 10 media creation tool
If nothing else, its a boot disc. There are other ways to get to advanced start up but this is the easiest on your hardware
Change bios boot order so USB or DVD are first, HDD is second
boot from installer, on the second screen - after language choices - select repair this PC, not install
Select Troubleshoot
Select advanced
Select start up repair - this will scan pc and maybe fix start up - will ask for logon details
another thing that might help is Safe mode
Use installer again, select repair PC again
Select troubleshoot/advanced/Start up options
Choose one of the 3 safe mode choices
PC should start in safe mode. Now often this is all that is needed but you could look in device manager and see if everything looks okay
If neither those work, you may need a reset.
Before you do, either move hdd into another pc and copy everything you want to save off it or try: http://www.howtogeek.com/howto/windows-vista/use-ubuntu-live-cd-to-backup-files-from-your-dead-windows-computer/
you can get to reset via the installer again, seleect repair this pc, and on first level of choices should be reset. Otherwise its hiding in troubleshoot or advanced
If your current install is an upgrade, you might consider doing a fresh install instead as they seem more stable. Here is how to do that: http://www.tenforums.com/tutorials/1950-windows-10-clean-install.html