Just further to my last post, I worked through another troubleshooting site (perhaps foolishly I turned to the ISP's site last!) and my PC connectivity issue's resolved.
Should anyone else have a similar problem as mine I followed advice at the VirginMedia support site, where they advise (for Windows XP) entering a netsh command.
This has subsequently changed my IP address and all's well ... until I try the XBOX again :/
I was wondering if anyone had any ideas with the following problem. My wireless internet has been working fine until I tried connecting my XBOX to XBOX LIVE. I've been using a Netgear wireless router, which is downstairs, to receive the internet on my PC upstairs. After trying and trying to no avail with the XBOX via wireless and ethernet to the PC, I disconnected the router from my modem and plugged the XBOX directly into the modem via ethernet cable. After a few fits and starts it worked fine. Only problem is, now my PC won't connect to the internet. It has the signal, I've used the Right-click "Repair" option (which it completes) and still nothing. I tried using Broadband Medic and it said the connection test and webpage loading both failed. My parents' laptop, which also shares this connection wirelessly, is working fine. I haven't put the XBOX anywhere near it since!
Systems wise my PC is running Windows XP Home Edition Version 2002 Service Pack 2, the modem is from NTL and the router is Netgear (the USB which receives the signal says WPN111 if that helps).
Sorry for the lengthy post, thanks in advance for any suggestions and please let me know if anymore information's needed.