Excellent article here:
Windows 7 Beta 1 will be made available for a limited time during the day on January 9, 2009.
Visit the Windows 7 page on Microsoft's website for the link. http://www.microsoft.com/windows/windows-7/
It will only be made available to the first 2.5 million people to download the code. Demand will be huge, so prepare to act quickly.
Microsoft has not announced a specific time on Friday for the release, but we can expect it will be later in the day so the west coast of North America isn't left out.
Windows 7 Beta 1 will be offered as an ISO image. It's around 2.5 or 3 gigabytes, so you will need a DVD burner if you want to install it.
You will be required to register before downloading so Microsoft can give you a product key.
It will be build 7000.
The beta will only support Windows Vista SP1 to Windows 7 upgrades. If you're not running Vista SP1 right now, upgrade before you try to install the Windows 7 beta.
There is also a clean install option for the Win7 beta.
There is no upgrade path from XP.
There's only one version of the beta, which Microsoft says "is roughly equivalent the Ultimate edition of Windows Vista."
The Windows 7 Beta will expire on August 1. You will probably be forced to go back to using Vista SP1 on August 1 (or maybe upgrade to Win7 Beta 2?).
English, German, Japanese, Arabic, and Hindi versions will be available Friday.
Both 32-bit and 64-bit versions will be available (except for Hindi, which only gets a 32-bit version).
If you're upgrading, remember to back up your PC. It's a beta, stupid!