Look at the upgrade to 64 bit. In Windows 16 bit days you had the C:\Windows\System directory. In Windows 32 bit, you gained C:\Windows\System32 for your system libraries. In Windows 64 bit you would assume C:\Windows\System64 right? Nope. 64 bit dlls go in to System32 and 32bit dlls go into SysWOW64. WTF?
Same goes with Program Files (32 bit) etc. They are pretty much screwed by legacy.
The windows mobile, XBox, and WinRT guys must feel so much better than having to work on Windows core because they don't have to deal with supporting 17+ years of software still running on their platform.
Have any companies of this size done this successfully? It would require a lot of work but could help them greatly in the consumer space.
Xbox is a good example of this working in a new cooler market , it has so few ties with microsoft that some of my 10 - 15 year old cousins who dislike microsoft don't even realize the xbox is a microsoft product.