Dell OptiPlex 755 - Manual (Page 73)

10. Skip the Un-Provision option. This option returns the computer to factory defaults. See Return to Default for more information about unprovisioning.
11. Select VLAN from the menu. Press <Enter>.
12. The following message appears:
l [VLAN Disabled] Enable VLAN: (Y/N)
Press <n>.
13. Select SOL/IDE-R. Press <Enter>.