QUOTE(lovethecold @ 6-12-05, 9:06pm)
I'm not familiar with this router, but here are a couple things to look at.
In the router setup screen, is there anything under WIRELESS SETTINGS for "Channel and SSID?" If so, select that and UNCHECK "Broadcast SSID"
Under firewall or any other option is there a "MAC address filtering" option? If so, get to that option and CHECK "Enable MAC address filtering". With it on, you'll need to add the MAC address of your own laptop and to get that
START button
My Network Places
View network connections (may be in the left sidebar)
Right-click your wireless connection
Select STATUS
Click the SUPPORT tab at the top
Click the DETAILS button
Write down the six pairs of characters that correspond to PHYSICAL ADDRESS. That is the MAC address of your wireless adapter in your notebook.
Those two should be a good start then see if your friend can find your network after a reboot? And if the network can be found and connected, see if sites can be accessed (I think MAC address can get an IP address, but not allow any traffic?)
Good luck!