Follow these steps to perform a Factory Reset using the Reset button on the back of the DI-804.
1. With the unit off, press and hold the Reset button with a pen or paper clip and turn the unit on.
2. Hold the reset button for about 5 or 6 seconds until the Power/Test LED on the front panel blinks very quickly and then release.
3. Wait a few seconds for the Broadband Router to reboot using
default settings.
http://www.dlink.se/support/techdocs/Manual_V.02.pdf
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