I just read on the Vista team blog site that all who subscribed to the CPP program back in June can start using Vista RC1. The Beta2 keys you received are still useable with RC1. So if you have a key download Windows Vista RC1.
If you are not part of the CPP program yet you can download Windows Vista but will have to wait until the CPP program opens for new registration (and it will open again).
You can download it from here : http://download.windowsvista.com/preview/rc1/en/download.htm. There are two options downloading using the download manager wich is the recommended way and if for some reason it doesn’t work you have the download with the browser.