Method 1:
Disconnect all the devices connected to the computer except keyboard and mouse and check if you are able to boot to the start screen.
Method 2:
If the computer fails to boot, try performing safe mode and perform clean boot.
Try to boot into Safe Mode with Networking. Press and hold the shift key while clicking on Restart at the login Screen (Bottom right corner).
•Select Troubleshootand click on Advanced Options.
•Select Startup Settingsand click on Restart.
•After restarting, choose Enable Safe modewith networking.
If the issue does not persists in Safe Mode, then perform a Clean Boot to check if any third party application is causing the issue, as Clean Boot helps in eliminating software conflicts.
Step 2
Put the computer in Clean Boot and check if it helps.
By setting your system in Clean Boot state helps in identifying if any third party applications or startup items are causing the issue.
How to perform a Clean Boot to troubleshoot a problem in Windows Vista, Windows 7, or Windows 8
http://support.microsoft.com/kb/929135
Note: After Clean Boot troubleshooting step, refer to "How to reset the computer to start as usual after troubleshooting with Clean Boot" from the article.
Method 3: You may try to boot from the Windows 10 media and try performing an Automatic repair from Windows Recovery Environment (WinRE).
To perform Automatic repair on Windows 10 computer follow these steps:
a) Insert the media such as (USB or DVD) and restart your computer
b) Press F12 key (typically this is F12, but it can differ between computer manufacturers) and choose the drive that you inserted the installation media into.
Once the Windows Setup window appears, follow these steps:
c) Click Next and select Repair your computer.
d) You will then see a blue screen and an option to choose. Choose the option Troubleshoot and select Advanced options.
e) You may choose Automatic Repair from Advanced boot option.
You may refer to the below link to download the ISO and create the installation media:
http://www.microsoft.com/en-us/software-download/windows10
Thanks and regards
Joy Kemprai