I have just moved into a new house which already has a Talk Talk broadband account. When i try to connect with my laptop (which has Windows Vista if that's of any significance) it says it is connected after i type in the password, but always comes up with the message saying that the modem or router is not available once i run the diagnostics. Everybody else in the house has no problem and my laptop has never had this problem anywhere else, so i'm unsure as to where the problem lies. I don't really know anything about this kind of thing but i've tried all the usual suggestions, turning the router off and on again etc. Any help would be greatly appreciated, thanks.

Try to use this ping tool to troubleshoot your network access problem, most likely it can help you to locate the root cause. Hope it helps.