As far as I know, only a "special" edition of XP Profesional, "special" being the key word here, will be released in 64 bits to complement Operton. Probably windows XP home edition will be released in 64 bits when the athlon 64 is released in September. I'm pretty sure The new 970 will be out by then, and panther will be released around september, or earlier. Could be wrong though.....iduno.
Windows, though, is a microsoft product so there isn't a reason to worry about it. It will probably take around 20+ service packs after it's released to have it working properley. It will have lots!.....lots!......lots!.......lots!......of bugs.
Operton will be a great processor, and if you whant to fully enjoy its power, get Linux!!.......
In my case.....I just can't wait to put my hands on one of those 970s....jeje