You can try the following. It may not work but if it does, it should get you to the troubleshooting screen. From there pick Advanced Options > System Restore. Restore to an earlier date. If that does not work you can refresh the computer but any programs installed since purchase would need to be installed. All your data would still be available after the Refresh.
- Hold the Power Button for 5 seconds or until the computer completely shuts off.
- Press the Power Button to turn the computer on.
- As soon as you see the rotating loading circle, press and hold the Power Button until the computer shuts off.
- Repeat this process 2 or 3 times until you see the Preparing Automatic Repair screen.
- Let the computer boot to the Automatic Repair screen.
- Click Advanced Options, and then select Troubleshoot.
If the above does not work then download Windows 8.1 media from here. Burn the iso disk and boot the install disk. See
Booting to Recovery Environment with Windows 8/8.1 installation media or Recovery Drive/System Repair Disc Here
Select Repair Computer and do a System Restore.