QUOTE
It looks like Microsoft removed the online registration for any beta products.
Generally, there are 2 main web sites (operated my Microsoft) that will allow you to obtain information about latest beta products developed by Microsoft Corporation:
www.betaplace.com and windowsbeta.microsoft.com
Microsoft currently maintains an open beta application process, in which anyone can apply for a private beta. However, a very small number of people are accepted for private betas, and there is no guarantee of acceptance.
Microsoft does, however, give preference to previous private beta testers when releasing new private betas. Once you are on Microsoft's private beta tester list, you will be contacted from time to time with applications for private beta test programs, according to their needs and your system configuration.
To submit your name for consideration for Microsoft private betas, send an email to betareq@microsoft.com, with the information below.
The subject of your mail should be the name of the product you are interested in beta testing.
If you are interested in testing multiple products, you must submit a separate e-mail for each product of interest so that they can quickly filter your request to the product team handling this program.
If the subject contains anything other than one beta product name, it will automatically be deleted by Microsoft's mail servers!
Do not put "Microsoft" in the subject line.
The email must contain the following lines (replace each line listed below with the appropriate field):
Name (First, Middle Initial, Last)
Company
Street Address (no PO Boxes)
City, State or Country, Zip
Phone
Fax
Internet address
Product interested in beta testing (if more than one, please submit separate e-mail requests)
Brief description of your hardware configuration.
If you don't get a response from the above email address (and most people don't), there are still a few ways you can get access to "limited" release betas. They're not exactly private betas, but you can get beta products faster than waiting for the public betas.