@ madsjm
They didn't really do anything to actively kill the Dreamcast, but when it was suffering after the release of the PS2, they certainly didn't try to help it or do anything that one might expect from the definition of "partner." Instead they used the experience to get a foot in the door for the XBox.
That's what Microsoft does with its parters - milks experience/technology, and then tries to corner the market with their own version of the partner's product. Had Sega not bungled their market position against Sony, I'm sure Microsoft would have made certain that they were squeezed out by the XBox.
