Hard reset D-Link DGL-4500

Factory reset (Hard reset) Power ON the router. Locate the reset pin hole on the back (next to the USB port). Press it with a thin object (paperclip) and hold down for 5-10 seconds. Release and wait for 30-60 seconds for the reboot process to finish.
Firmware Firmware link
Default username admin
Default password [leave blank]
Default IP address