Providing you reset the router by sticking a pin in the back hole for about 10 secs. till test light blinks, the default username/password should be admin/password. Change password to a harder one immediately.
Use Wireless Settings to set recommended Authentication of WPA2-PSK(Wi-Fi Protected Access 2 with Pre-Shared Key) with a difficult key.
EDIT: You might need a more recent version of firmware for this method.
1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU BB => 2010: Orange 16 Meg LLU BB
Edited by XRaySpeX (Sun 30-Jan-11 19:45:13)