Mark’s Sysinternals was playing around with RootkitRevealer and discovered that Sony installs its own media player on your PC, reroutes windows systems calls and hides itself to limit the amount of copies that can be made of the disc. Now you could call it DRM I guess, but if you try to remove the modifications it made, you end up breaking your windows installation, which nothing short of a format and re-install will fix. Begad, it’s a rootkit virus!