Mark Rasch, an IT lawyer, has a wonderful essay on the problems raised by the Vista EULA. The nub of it is this:

The terms of the Vista EULA, like the current EULA related to the “Windows Genuine Advantage,” allows Microsoft to unilaterally decide that you have breached the terms of the agreement, and they can essentially disable the software, and possibly deny you access to critical files on your computer without benefit of proof, hearing, testimony or judicial intervention. In fact, if Microsoft is wrong, and your software is, in fact, properly licensed, you probably will be forced to buy a license to another copy of the operating system from Microsoft just to be able to get access to your files, and then you can sue Microsoft for the original license fee. Even then, you wont be able to get any damages from Microsoft, and may not even be able to get the cost of the first license back…

Worth reading in full. Many thanks to Chris Walker for the link.