There are just as many issues with XP if you google the same thing - there's not much substance to that arguement.
However, I recommend you do not reinstall Windows from the factory settings. If there's some application the manufacturer installed that's preventing all this (a firewall seems most likely), installing Windows from a fresh OEM version will cure that. Vista has no previsions for blocking certain types of connections and programs...only Windows firewall does (which is a part of XP, too).
Have you installed XP on this machine before and used it with success? I suppose we can't rule out a malfunctioning network card, but that seems incredibly unlikely.
Also, with your antivirus and other software down (and apparently no presence of a firewall to block specific connections) malware seems also a likely culprit for your problems. The clean OEM install should fix that, but if you want (and have another computer), you can always do a third-party scan.
On another note, has the machine always done this from when you pulled it out of the box?