If this is the first connection outside your home network that does introduce more uncertainty.
In case you are trying to connect to your network at your friend's place in error here is MS' procedure:
1. Right-click the network connection icon in the notification area, and then click View Available Wireless Networks.
2. In Connect to Wireless Network, under Available Networks, click the wireless network that you want to connect to.
3. If a network key is required for Wired Equivalent Privacy (WEP), do one of the following:
• If the network key is automatically provided for you (for example, the key is stored on the wireless network adapter given to you by your administrator), leave Network Key blank.
• If the network key is not automatically provided for you, in Network key, type the key.
4. Click Connect.
5. To configure additional wireless network connection settings, or if you are having difficulty making a connection to the wireless network that you selected, click Advanced, and then configure the settings in the Wireless Networks tab.
When you look at the list of available networks on your laptop, is there just the one network shown, which is hers? What method of security is shown, WPA or WEM? Are you positive her password/key is being typed in exactly as it should be?
When you got to the username and password you should have looked at the list of passwords that I gave you the link for. It's probably admin and admin or, nothing at all and nothing at all (blank and blank).
I can't find a WRT1320N manual at Linksys so this is based on others and I can't read the images properly on those so best guess:
If you get in, go to Advanced Configuration? Network Setup > Network Address Server Settings (DHCP)
DHCP should be enabled and probably start at address 100
Wireless > Security Mode
Make a note of which security method is used (WPA or WEM) - is it the same as when you tried to connect?
Wireless > MAC Filter
Is this disabled?
If enabled, is it Permit Only?
If enabled press the button to get the list and check there is at least one number in the list (your friend's PC)
Post back what you find