I don't think this has anything to do with companies that offer services around Microsoft products - this will be about the Microsoft subsidiaries and assets located within the EU - there will probably be at least one Microsoft legal entity within each country where they have a direct presence, not to mention significant assets like large data centers.
That's an issue those people would need to take up with Microsoft if Microsoft decides to risk their business over this. If they don't pay, they will have assets frozen, just as any other company or individual that refuse to pay their fines. Simple as that.
I know they will back down, but it makes me wonder; what if they didn't?
Could a business, a corporation, go to war against another entity. Countries go to war all the time and while it may be "illegal", it's only the loser that has to suffer the consequences.
What if Microsoft just decided screw it, and flipped a magic switch somewhere and shut down the entire EU infrastructure. No OS, no web servers, no SQL, no sharepoint, etc. Trashing or stealing every bit of data along the way? Freeze Microsofts assets you say? What if they could freeze or steal a great portion of the EUs assets?
Sure, the EU would get over it eventually, but it's an interesting thought experiment.
Unpaid fines continue to grow. Eventually it would perfectly within reason to seize (take) Microsoft's copyright on windows making piracy perfectly legal.
I seriously doubt MS will commit seppuku over a fine. Which is really what scoffing at this would get them.
More than likely, they'll roll out changes to their browser preferences now (that they've been caught red-handed) and maybe include a "browser bundle" that has Firefox, Chrome and IE in newer versions and recommend OEMs deploy the same. Naturally it may still default to IE if the user clicks "next". That way, they can maybe negotiate down the overall sum of the fine saying "hey, sorry we're late, but look! We're doing the changes."