Use this tutorial :
Link Removed
It shows you how to go to Safe Mode in Windows 8 and 8.1
Go over the tutorial once before you start.
In that tutorial, you will see an option to do System Restore.
Try that route first. Pick a good date when you did not have this problem as your restore point.
After it is done, find out if you can login to your admin account in Normal mode.
Please post back the result before I continue.
If that does not work for you, then we'll have to continue with the tutorial and go to Safe Mode with Command prompt.