Boot the DVD & open a Command Prompt.
1. Click Command Prompt from the System Recovery Options window.
2. In the Administrator window, type the following lines, pressing <Enter> after each line.
3. In the Dell Factory Image Restore window, click Next.
4. In the Confirm Data Deletion window, click to select Yes, reformat hard drive and restore system software to factory condition, and then click Next. The message Factory image successfully restored! appears when the process is complete.
5. Click Finish to restart the system.