Help required with new wireless etup

[giantsf49er]

Im trying to sort out my mother onto a wireless internet set up and am having problems.

She has a 2MB connection through her 2100C STB. This runs into an RJ45 jack on the wall. From there its wired oround the outside of the house to another RJ45 wall socket in the computer room. From there RJ45 straight into the PC.

We have bought a Linksys WRP200 Wireless G and VOIP router. We wired it in downstairs between the STB and the RJ45 wall socket. Lost ALL internet. No wired connection to upstairs, no WIFI connection. Thinking it might be an issue with x-over wires I unplugged the router and went back to the original 2100C to wall connection but using the new wire from the router. Internet back on. So the wires arent an issue.

Then tried moving the router upstairs and setting it up inbetween the RJ45 wall socket and the PC. Same reusults, no wired connection, no WIFI. Gone back to original setup and everything is fine again.

Does anyone have any experience of using the WRP200 router at all? Despite it being Linksys Im having trouble finding a whole lot of information about it on the internet.

Any advice would be greatly appreciated.

Thanks

[MovedGoalPosts]

Have you powered the Set Top Box (STB) off when you connected up the router? It won't detect the router unless you do. When you reboot the STB you'll need to register the router with the STB's provisioning system. When you first browse the internet you should be redirected to the registration server.