Windows 7 If your into the Beta thing you better grab it. It went live again about an hour ago and is only supposed to be open to 2.5 million users. I grabbed the 64bit version from a direct link last night, it will install without a key but won't activate, been using it since. It's NICE. Running on my old computer BETTER than XP! It's good until Aug with the keys MS is handing out.