Some sad news for fans of PC gaming with word that Direct X 10 will only work for the next release of Microsoft's wonderful operating system, Vista. It had previously been rumored in the darkest corners of this vast Interweb that graphics card manufacturers wanted to put off Direct X 10 in order to give gamers the best possible graphics. Now we know it's true.
Apparently, the main reason why you won't be able to use Direct X 10 is because Windows XP's driver model doesn't mesh with the presence of more independent objects. Of course, no final Direct X-compatable hardware has been released yet, so there's no telling if this new API will really do anything special, like make world peace.
Direct X 10 will be Vista only [The Inquirer]