WEP encryption is next to useless now, it's totally been cracked. Also it doesn't matter if you forgot the key. Simply log on to the router (as long as you know the user/pass) and change the key. I would recommend going to WPA-PSK if your router and nic's support it, if your running winXP (sp2) the windows wireless configuration already supports WPA. If your router doesn't support WPA but you want a secure connection to the internet try downloading ipig software it's free and secures you in a VPN type connection.
Hope that helps
BullDog(UK)