Set up WEP encription is the normal way. Password access to the router so they dont enter it and simply copy the WEP key. They can hack into it though if they really want to.
Or buy a new router with WPA encription and use a 20 letter passphrase.

Mikie...how do I go about doing this until I get around to buying a new router? I went to Linksys' website, but I don't have the "Wireless" tab they refer to in the instructions, and the instructions say they are for this router! I don't want to change something and then not be able to connect to the internet! When I do this will I then have to reconnect or reset some sort of settings to get on the internet?

Thanks!

Do you see a link on one of the setup pages for WEP or wireless Security ?

Think 31 characature max passphrase, but might start with something simple like brownDog then change it after youre all up and running ok.

I'd choose 128 bit
Then Default key number 1

Then copy and paste all the keys onto notepad, save it and have it on your desktop before pressing the OK/Apply or whatever it says.

Windows xp will then pop a box showing the available wifi connections and you choose the one with your ssid, copy and paste that #1 key into the little windows text box.. Connect. (cross your fingers ;)

If for some reason windows cant connect, you can always take a paperclip and reset the router to defaults ... or hook up a network cable to get back into it on a wired connection if you have a lot of settings you dont want to luze.

Here's a link to the User's Guide for this router:

Here is a link that might be useful: BEFW11S4 User Guide