But what about Windows?.............. if you buy an OEM version then Microsoft will tell you to talk to the computer manufacturer, but will they support it without charge under their general warranty?

I wonder if anyone will answer?............remember that here in the UK, there are three interesting statutory, or statutorily empowered bodies:
At lenovo/IBM thinkpad support, we will not support windows without a fee, or most software for that matter... as I posted earlier, we provide very very basic support for the thinkvantage technology [TVT] suite, but nothing beyond where to download, how to uninstall, reinstall, and if that fails, we are supposed to tell the customer to reload windows... I hate that. absolutely hate that policy... we are supposed to be done with calls in 11.5 minutes, but if it goes longer, they understand... as long as simple calls aren't lasting 45 minutes... and as long as you follow the correct menu prompts: 1, 1, [four digit] machine type, 1 ... your hold time will generally be less than 60 seconds... in fact, that is contractual... we have to have an avg hold time of <60s ... pretty good for tech support in my opinion...