This excerpt taken from the WDC 10-K filed Nov 20, 2006.
The PC market consists of the overall hard drive market for desktop and notebook computers. Consumers use PCs in homes, businesses and multi-user networks. PCs use software applications for word processing, spreadsheet, desktop publishing, database management, multimedia, entertainment and for other needs. Hard drives store both PC software applications and the data used by the applications.
We believe that the demand for hard drives in the PC market has grown in part due to:
We believe several other factors affect the rate of PC unit growth, including maturing PC markets in North America and Western Europe, an increase in first-time buyers of PCs in Asia, Eastern Europe and Latin America, and the lengthening of PC replacement cycles.