Managing hardware diversity

Generally speaking, each additional hardware configuration in a desktop environment costs an additional $12 per computer in yearly support, according to an Intel white paper about the Benefits of Controlled PC Hardware Diversity. http://itpapers.techrepublic.com/abstract.aspx?docid=96008 The paper bases its statistics and recommendations on a study based on U.S. companies and associated labor and hardware rates. Have you established a method for controlling the degree of diversity in your company’s hardware?