I'm a little curious what the EU did that was actually effective here, though? Because the things I mentioned are all things that look a lot like new markets growing outside of the one MS owns, and MS being unable to adapt.
I remember the EU doing that whole browser ballot thing awhile ago, but that was long after MS started losing the browser war. They thought they won with IE6, and it kinda looks like they stopped development. Then we got Safari and Firefox, and then we got IE7. Roughly, MS seemed to be taking about 2 years between IE versions, but there was 4 years from IE6 to IE7, and my theory is they saw Netscape die and figured they were done and could stop investing in IE... and then started again when Firefox showed up. And IE7 is exactly 2 years after Firefox... Firefox 1.0 was 2004, and the EU's browser ballot didn't show up until 2010, when IE marketshare was already falling... due to competition. Maybe the EU helped it along, but IE's downfall was pretty inevitable at that point.
Because Firefox and Safari really were better. IE6 didn't even have tabs! And Firefox had a built-in popup blocker, enabled by default. And Firebug was ridiculously better than the MS script debugger, so if you were a web developer, you worked on Firefox, and only booted up IE when you had to test the site. So people (especially web developers) started picking up these browsers, and caring about web standards, and by the time the browser ballot showed up, the entire industry hated IE and wanted it to die.
There's a similar story with applications moving to the Web. People didn't do that because the EU told them to, they did it because it has a ton of advantages:
if you're a user, there's nothing to install and you can use it anywhere, which was a big deal before smartphones were ubiquitous -- if you're visiting someone's house and you want to check your email, you use their computer and login to hotmail, or later gmail. And the browser sandboxes it for you, so it's also not as risky as just downloading some random app, especially in the days before app stores.
If you're a developer, you get more users to try your thing because you don't have to convince them to install anything (and then walk them through how to run an installer in the days before app stores), and you get a bunch of free UI built in that your users already know how to use (links, tabs, back/forward, refresh if it breaks), you get free autoupdates, cross-platform support, and you can build the backend (server) on anything you want.
Then there's mobile. That's an even simpler story: MS was already building things like pocket PCs running Windows CE, which can (appropriately) be abbreviated WinCE. But the iPhone came out with a completely different UI model that meant all your apps (from WinCE or Windows) would have to be redesigned -- there's so many apps where you don't want anything like the same app you have on the desktop.
So MS didn't have any sort of dominant position in mobile at the start... or ever. They thought they'd at least repeat the PC's business model, and license their OS (cheaply) to a bunch of different commodity hardware manufacturers, and flood the market with cheap PocketPC clones...
But Google undercut them with a free OS, and a business model that doesn't rely on making money from licensing copies of the OS. And by the time MS might've adapted Windows Mobile to deal with this, it was too late -- iOS and Android were so far ahead that MS ported all their big apps like Office, long before they gave up on Windows Mobile entirely.
Finally, the server. MS never really owned the server, their only real advantage is people really like Visual Studio, and it's easier to port a legacy Windows app (especially a .NET app) to a web app on Windows Server... but it turns out that neither of these were compelling enough, compared to the alternatives: Any idiot could put together the LAMP stack (Linux, Apache, MySQL, and PHP), and even if Windows Server was probably technically superior (MySQL and PHP are pretty awful), the open source option is cheaper to start and cheaper to scale.
And with these things driving web apps more and more... it's easy to build the glue you need to connect any language you want to a webserver. HTTP isn't hard, and you can use a reverse-proxy to handle the parts that are. So you could do Linux, Nginx, Postgres, and Ruby, or any number of other combinations. That's true of Windows, too, but MS only had a monopoly on ASP, .NET, and VB. If you wanted to build your app in pretty much any other language, you could make it work on Linux, save a bunch of money, and make your sysadmins happy.
So Linux pretty much won servers, to the point where MS had to add Linux compatibility to desktop Windows, just so programmers who work on Linux servers would start buying Windows laptops again instead of Macbooks!
I don't mean to say the EU's behavior is pointless here. Sometimes you really do need regulation. I just don't think regulation is the reason MS is losing so badly now, in the markets it's losing, partly because I don't see a way for MS to leverage their Windows desktop monopoly (or even their IE marketshare) to change any of those stories.
In fact, in a couple of those stories, we see exactly how MS tried and failed to do exactly that. IE6 was incompatible with web standards, and at first there were a lot of "works best in IE" sites, but by the time the EU did anything serious about it, IE was already losing.
