Currently Being ModeratedFeb 16, 2013 11:13 AM (in response to twhiston)
There are at least 4 versions of the AirPort Express, and only the two most recent versions have the capability to "extend a wireless network".
Which version of the the AirPort Express do you have? If you have an older version, check the Model No on the side of the AirPort Express. You need to see A1264 there.
If you have the "new" AirPort Express.....it looks like a miniature Time Capsule.....that device will work as well.
Post back to let us know what you have so we'll know how to proceed.