Re: My approach
> What I don't get is this: If your warranty is expired, you don't care whether they say your warranty is invalid if you use non-Microsoft (or whatever) parts. If your warranty is in force, why would you make repairs using third party parts, instead of having the vendor repair it for free?
Couple of examples:
Bigger HDD in the Games consoles than what they shipped with. Microsoft and Sony were refusing warranty repairs for any problem, even those totally unrelated to the HDD, if a non-genuine HDD was used.
They put illegal "warranty void if removed stickers" on components, so even if you opened a case to say clean out the dust build-up, they were refusing warranty service because it was opened and the stickers removed/tampered with.
Or, for example with the cars, putting an after-market more effective airfilter in, or a custom stereo, or non-genuine brake pads, all of those were claimed to be grounds for rejecting warranty service for unrelated issues.
The issues weren't to do with claiming warranty repairs on parts already replaced/modified/upgraded with non-genuine parts or 3rd-party repairers. It was claiming warranty for totally unrelated issues, and these companies were either refusing to provide that warranty service, or at least were wording their warranty Ts&Cs such that it looked like they were claiming that.