What might be even easier (and more secure; free tools can crack the WEP encryption in 5-10 minutes) way to do this - enable WPA if it's available. You just enter a passphrase and enter it into your wireless clients. If this doesnt work on the wireless end, then it means that you are stuck with WEP.
"Know this, you can cut me off from the civilized world, you can incarcerate me with two moronic cell mates, you can torture me with your thrice daily swill, but you can not break the spirit of a Winchester. My voice shall be heard from this wilderness and I shall be delievered from this feted and festering sewer." - Charles Emerson Winchester, III, M*A*S*H