Given the number of documented malware-like tricks (deceptive buttons, hidden options, X that means "accept", disguised and misrepresented patches, unable to disable without additional software etc.) The should have jst turned updates off argument won't stick.
As for the eula $5 limit... doesn't wash and isn't legal in a good chunk of the world as it can't trump the consumer rights laws especially when the product is actually retail priced around 25x that value.
Finally while people say "Which? is just a consumer rights group" should realise that they have a very good reputation both with consumers and with Trading Standards (or whatever they call themselves these days, stupid government "rebranding") in the UK who are the legal authority that could force Microsoft to compensate (either directly, or through the courts depending on the specific situation). There have been many Which? articles in the past that have progressed into full on legal sanctions to companies.