To play one of the Sony CD titles on a PC, you must first accept Sony BMG's licensing agreement and a software download, which includes the Sony music player and the hidden files that have become prey to hackers. You can't take the stuff off your computer without Sony's permission.
Apple uses its own DRM method for digital music, which it calls FairPlay. It's led to much consumer confusion, due to a basic stance of Apple's business policy. Apple won't license FairPlay to other companies, so rivals in digital music are forced to use other DRM tools — most notably Microsoft's Windows Media.
And just like VHS and Beta, Apple and Windows, and other incompatible formats, songs in Windows Media won't transfer easily to the iPod, and FairPlay tunes won't play on non-iPod devices.
No entity has taken bigger hits in the DRM debate than Sony BMG Music. When Russinovich first blogged about the issue, he showed that some of Sony's copy-protected discs had hidden files, called "rootkits," that potentially could be used for viruses. Sony initially responded by posting a downloadable patch on its website, which makes the file visible on a hard drive.
from USA Today.