Early Thursday, Microsoft opened the doors to all comers who would like to test Windows Vista Release Candidate 1 (RC1). Testers can access the 2.52GB of data that makes up the next version of Windows either via download or on a DVD that will be sent in the mail.

To initiate either process, would-be testers should visit the Vista Get Ready page and click the "Get Vista RC1" link (http://www.microsoft.com/windowsvista/getready/default.mspx).

Before Thursday, only previously registered members of the Microsoft's Customer Preview Program (CPP) -- the 1.5 million people who accessed Vista Beta 1 in the same fashion earlier this year -- were given access to RC1. Although Microsoft hasn't officially announced the number of new CPP registrants it will allow for RC1, some Microsoft executives had previously estimated that the number would reach an additional 1.5 million testers.

Those who request the DVD to be mailed to them will be required to sign in with a Microsoft PassPort (not called Windows Live) e-mail address, answer some demographic questions and pay US$5 in the U.S. for media and postage. Delivery will take two to four weeks.

Windows Vista is due out by early next year.