I hope that you made a back up of your database first. For starting, get your computer restarted. As soon as, it restarts, press the F8 key to jump to the Advanced Boot Options before that the Windows logo is displayed on the screen.
Now get to the Repair Your Computer option and press enter and get through the simple wizard that will follow. The next step will be logging as an Administrator and select Dell factory Image restore. On the following box, please click on Next and then check the box for Reformating Hard Drive and hence you will have your system restored to factory settings.
Make sure not interrupt the task for it might cause damage to your system.
Good luck and if you need more information, do indicate.
Have a nice day.