When will Microsoft open up their OS to customisation?

One way Microsoft could improve their strategy is to offer users and PC sellers choices in the way the OS is setup, what components are installed and what browser, Wordprocesor is setup as default etc. Even more useful things like what UI is default and the ability to run a different desktop such as Gnome or KDE. It would give Microsoft another chance to compete with the flexibility that a GNU+Linux PC seller has. The EU Competition Commissioner Neelie Kroes may even force them to open up their OS to vendor customisation when they loose the Opera case..? It would save them market in the short-term.. so let's hope they don't read this!