Microsoft Account users can reset their password on login.live.com. Users without a Microsoft Account must either use a Password Reset Disk or restore or reinstall the computer's operating system.
On the Microsoft Account website, you can reset a lost or forgotten password by answering some security questions and entering a new password.
If you have a Password Reset Disk, go to the Windows log in screen, click Reset Password, insert the Password Reset Disk and then follow the instructions on the screen.
If none of these options are available, you must reinstall your operating system or restore it from a previous backup. Dell.com provides instructions to restore an operating system.