Try starting it up in "Safe Mode" and see if it will load. If it does, then you probably have a virus, malware, etc., on the computer you need to remove. Should that not work, then I would check your BIOS and make sure that the drive with Windows on it is actually the first one listed. If it isn't, then move it to the first position and try starting again. If, however, it still won't load, then either the OS is corrupt or your hard drive may be going bad.
How to enter "Safe Mode" when booting the computer.
In Windows 8 and 10...
As your computer restarts, press F8 (possibly a few times) to enter "Safe Mode"
a. Press the "F4" key to Enable "Safe Mode".
(The computer will then start in "Safe Mode" with a minimal set of drivers and...