Clearly, you never read the EULA, or even the Warranty statement.
Microsoft only promises that it will work as intended for the first 90 days after it's installed. After 90 days, if Microsoft decides to tell you to piss off, you're SOL, because the software is presented to you AS-IS.
During the warranty period, if you have a problem, Microsoft will, AT THEIR SOLE DISCRETION, either refund the money you paid for the software (if you actually paid anything for it. If it came preinstalled on your computer, you paid nothing for the software - the computer maker did. You have to talk to them) or they can choose to fix the problem.
If you're outside of the warranty period and you don't have an active support contract, Microsoft doesn't have to care about your problems at all.