Example: Electronics Arts games do not run on home systems where a Digium TDM400P card is installed. Even though the card provides an interface to the telephone system for a *BSD or *nix system, on the Windows side it is an unknown and, therefore, must be some sort of hacker tool for defeating copy protection. The end result: your EA Games game is disabled by its DRM and you, as the end-user, have no recourse other than to remove the phone card or stop playing the game.
Can we hope that Windows DRM will be any different? It isn't Microsoft's intellectual property that the Vista DRM is protecting. (At least I hope not. That'd involve a large set of really nasty anti-competition court cases that I hope no one wants to get involved in.) Those IP owners that the DRM is actually protecting care little about whether or not your systems work properly.
OS and hardware vendors are in for a very bumpy ride because legions of frustrated innocent bystanders (such as in the above example) will be left with no recourse other than to "conform" with the masses and stop using their systems to do anything other than play games and buy content.
(Yeah, I excluded Office apps. I did this because we already know that documents have unique IDs embedded in them. How long until Vista's DRM is used to disable licenses of controversial content authors? With Vista's DRM, the only thing keeping this from happening is: morals/ethics/ignorance of the ability.)