@Balmer: Get rid of .NET. There are people who use it, and some of them actually like it, but it will never become the huge success you thought it would become. This also means Silverlight has to go. The JIT compiler, with an open sourced assembly language, could get a 2nd life in the browser.
For a next OS, have a good long look at Windows 2000. Start from there, and instead of adding millions lines of code, start rewriting to make it smaller and faster. That way you end up with a valid OS to use on mobile devices.
Put more effort into your webbrowser. Make it so that it can be used for any type of application. Don't wait for W3C, if it's up to them we will have to wait till 2019 for a complete HTML5 specification. The other browser developers will either follow, and if not, developers will decide if they make a windows only application. Make the browser the default UI layer of Windows. This time to prevent nasty lawsuits, make it easy for others to add their own navigational toolbar.
So in short, instead of trying to protect business with windows locked in technology, be more open, and out develop the other companies. Become the company again, where it pays off to develop on your platform.