go Start then Run in XP - (Windows key plus R in Vista and Windows 7), then type in the following, including all the spaces:- cmd /k ipconfig /all -- then press Enter and from the black form that shows up, take a note of the numeric code beside the word "gateway" -- usually something like 192.168.0.1. Type exit to close the black form.
connect a computer to the Linksys and log in
setup the wireless security and save settings
disable DHCP and change the LAN IP to match the gateway IP scheme but ending in 253, and save settings
finally connect one of the four LAN ports to your main router.