Power everything down.
First of all the cablemodem will plug into the back of the wrt54g. into the Internet port or the WRT54G.
The WPC54g will go into the Laptop, and the WUSB54G onto the Desktop.
Wait 30 seconds then power up the CM first. Wait until diagnostics has run and modem is ready. Now power on WRT54G, leave it to do its diagnostics etc., for a couple of minutes.
For setup purposes of the WRT54G i would strongly advise you to first add the laptop to the port 1 on the WRT54G using the ethernet connection. this is so you can setup the wireless side of the Router first of all.
to get to the setup open you browser and type 192.168.1.1
username: root
password: admin
then you will see the setup of the WRT54G. goto wireless.
http://192.168.1.1/Wireless_Basic.aspset wireless mode to G only
SSID to whatever you like.
Channel 11 seems to be overall best.
as to enabling SSID i would use this to start with....
click on save settings
then click on next tab Wireless security
Set to WPA PreShared Key
AES
and a password of your choosing
group renewal 3600
Then click on save settings.
Now exit router setup. and disconnect router from laptop. now plug in WPC54G and setup the drivers. a reboot may be required.
Once rebooted then you'll need the WPC54G software to reconsing the wireless connection by adding the WPA PSK, AES and Password settings to it.
Once this is done you should be able to surf ok then using the laptop.