Usually, new software enables you to do more with your computer. Vista, though, is designed to restrict what you can do.

Vista enforces new forms of “Digital Rights Management (DRM)”. DRM is more accurately called Digital Restrictions Management, because it is a technology that Big Media and computer companies try to impose on us all, in order to have control over how our computers are used.

Technology security expert Bruce Schneier explains it most concisely:

Windows Vista includes an array of “features” that you don't want. These features will make your computer less reliable and less secure. They'll make your computer less stable and run slower. They will cause technical support problems. They may even require you to upgrade some of your peripheral hardware and existing software. And these features won't do anything useful. In fact, they're working against you. They're digital rights management (DRM) features built into Vista at the behest of the entertainment industry—And you don't get to refuse them.