Windows 7 was launched on October 22nd, and is now available at all retail stores near you.
In case you need to change your Windows 7 product key, there are two methods to do so. You can do it from System Properties or from DOS using the commands.
Windows 7 M3 (build 6801) was leaked over the Internet through torrents a few weeks ago, which was free and easy to download. But you still need a valid activation product key in order to use Windows 7 on your system or you will only get a 30-day trial.
Later it was found that the old Windows Vista Beta and RC product keys can be used for Windows 7 Pre-Beta as well and you can activate your copy using it.