Dell Studio 1535 (Mid 2008) - Manual (Page 51)

Troubleshooting
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6 Click Dell Factory Image Restore.
7 In the Dell Factory Image Restore window, click Next.
8 Select the Yes, reformat hard drive and restore system software to factory
condition checkbox.
9 Click Next. The computer is restored to the default factory configuration.
10 When the restore operation is completed, click Finish to restart the computer.