I don't think having a fixed OS made by MS for music apps is a good idea. This would allow MS to charge any price for the OS, and there would be no competition to keep MS fixing bugs, adding new features, and shipping new versions of the OS.
Take a look at BeOs. This OS is just starting out, and if MS isn't careful, this new OS could create a nitch within the music and graphics community, and, although not hurt MS's market share, it would make MS create a better product.
WE need the competition.
I think the major problem is that hardware companies are not creating software that complies with the set standards laid out for their hardware. PCI display adapters are a prime example of this.
This is why most of the new "cutting-edge", "full-featured" sofware apps were created on the Mac first, and then the PC. The Mac has a closed system that is the same for just about every Mac.
I, personally, like using PC's more than Mac's. But, then agian, I'm just a nerd.