Vista EULA Agreement...

"The EULA ominously warns that “Before you activate, you have the right to use the version of the software installed during the installation process. Your right to use the software after the time specified in the installation process is limited unless it is activated. This is to prevent its unlicensed use. You will not be able to continue using the software after that time if you do not activate it. ” What does this mean? Essentially, if you buy a license to the software from a reputable dealer, but choose not to transmit information to Microsoft, you forfeit your ability to use the licensed software.
What is interesting is not whether you have the right to use unactivated-but-properly-purchased software, but how Microsoft enforces its right. What Microsoft says is that the software will simply stop working. So, where is the proof that the software is not activated? Who has the burden of proof? What if you assert that you did activate the product, but Microsoft claims you did not? What if you attempt to activate the product, but Microsoft’s servers are down, or they provide improper information, or their servers are hacked and give you bad activation information? What the contract states is that unless you can activate the product (irrespective of whose fault it is that you cannot activate), you forfeit your right to use the product, and therefore access to any of the information on any computers using the product. "

Much, much more: http://www.securityfocus.com/columnists/423/1