Can I play Guitar Hero or Rock Band on my PC?
Several of the Guitar Hero games have been released for Windows and Mac, including Guitar Hero III, Guitar Hero: World Tour and Guitar Hero: Aerosmith, and USB-based instruments should work natively with them. None of the Rock Band games have been released for PC, however, and intercompatibility is generally bad.
Try Frets on Fire for a free and open source Guitar Hero-style game which works with all the console instruments. For full details, drivers, and the like, see the Frets on Fire Wiki page on using Guitar Hero and Rock Band controllers. Many of the Guitar Hero and Rock Band series songs have been converted for use with Frets on Fire, and there is an enormous base of user-created content: see the wiki for details on available song packs.