Why does my computer stop our home wireless broadband?

I have an IBM T41 ThinkPad, it has Microsoft Windows XP Professional installed on the hard disk and has all of its original software and hardware. It has, however had the built in software and OS complete recovery program run twice as a result of change of ownership between myself, a school and the original vendor. When ever the computer is powered on, including when it is in stand by mode, our home wireless broad band is cut off. The computer can not connect to this network, we have tried that, but along with this if the computer is on, no one else, on the other house hold computers or the iPad can connect to the wireless. It also has the same effect on the Ethernet port on the modem. Another extreme of this is that it also knocks out the 3G network to one of the iPad and iPhones.
I have know idea what is going on with this and hope some one can help me, I have given pretty much as much information on it as I can.
I have a reasonable capability with computers especially with this one but I simply can't figure this one out.
Thanks.

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