Sometime wireless management is disable for security reason. So a computer connected with wireless won't be able to manage the router. You'll probably have to enable the feature if you want to.
Check these out from Netgear
WGXB102 - NETGEAR.com
There are two devices, the XE102 is what plugs into your router and the power outlet creating a LAN and the WGX102 plugs into the power outlet to create the extended wireless signal.
You can buy more WGX102 to extend your signal even further in your home but you only need 1 XE102.