numerous failed attempts in the early 1990s, and several years of development. Mac OS X was based on NeXTSTEP, OPENSTEP, and BSD Unix, with Apple aiming to combine the stability, reliability, and security of Unix with the ease of use afforded by an overhauled user interface, heavily influenced by NeXTSTEP. To aid users in migrating from Mac OS 9, the new operating system allowed the use of OS 9 applications within Mac OS X via the Classic Environment. In May 2001, the company opened its first two Apple Store retail locations in Virginia and California, offering an improved presentation of the company's products. At the time, many speculated that the stores would fail, but they went on to become highly successful, and the first of more than 500 stores around the world. On October 23, 2001, Apple debuted the iPod portable digital audio player. The product, which was first sold on November 10, 2001, was phenomenally successful with over 100 million units sold within six years. In 2003, Apple's iTunes Store was introduced. The service offered music downloads for 99¢ a song and integration with the iPod. The iTunes Store quickly became the market leader in online music services, with over five billion downloads by June 19, 2008. Two years later, the iTunes Store was the world's largest music retailer. In 2002, Apple purchased Nothing Real for their advanced digital compositing application Shake, as well as Emagic for the music productivity application Logic. The purchase of Emagic made Apple the first computer manufacturer to own a music software company. The acquisition was followed by the development of Apple's consumer-level GarageBand application. The release of iPhoto in the same year completed the iLife suite. At the Worldwide Developers Conference keynote address on June 6, 2005, Jobs announced that Apple would move away from PowerPC processors, and the Mac would transition to Intel processors in 2006. On January 10, 2006, the new MacBook Pro and iMac became the first Apple computers to use Intel's Core Duo CPU. By August 7, 2006, Apple made the transition to Intel chips for the entire Mac product line—over one year sooner than announced. The Power Mac, iBook, and PowerBook brands were retired during the transition; the Mac Pro, MacBook, and MacBook Pro became their respective successors. On April 29, 2009, The Wall Street Journal reported that Apple was building its own team of engineers to design