First of all, you need to consider backing up your important data, as the system restore process will erase all your data present in the computer. For that purpose, you can connect any external disk drive with your computer, which you will use to back up all your data.
Now open “Control Panel” from the “Start” menu and double click on the "System and Maintenance" or “Performance and Maintenance” icon, depending on Windows version installed in your computer. A new window will now appear on your screen. Again depending on the variant of the Windows installed, click "Backup and Recovery" or “Back up your data”.
Now you need to follow the onscreen prompts on the “Backup or Restore Wizard” to backup all your important data on the external drive that you connected with your computer. Disconnect your external drive from your computer.
Once you are done with backing up your important data, restart your computer and press “F8” key at system start-up and you will see “Advanced Boot Options” menu appearing your screen. Use your arrow keys to highlight the “Repair Your Computer” option and press the “Enter” key.
Login using administrator account and select the "Dell Factory Image Restore" option from the list of options that appear. Click the “Next” button to proceed.
You will now be asked to confirm whether you want to restore your system. Here, you need to click the “Yes” button, and then the “Next” button.
Your computer will now take some time to restore your computer’s operating system to its original state. Once the process is finished, you should click the “Finish” button, and your computer will automatically restart.
Once again, connect the external drive with computer and copy all your data back to your computer’s hard drive.