Due to network externality, certain standards tend to dominate in areas where compatibility does not exist among competing products. Nevertheless, certain trends are not easily explained by network externality alone. One example is the domestic PDA (Personal Data Assistant) market, in which the share of WindowsCE, most effectively linked with Windows-based PCs and supposedly the most advantageous in terms of network externalities, retains only a small market share, particularly among personal users. Kurimoto & Kobayashi (2004, 2005) have demonstrated that such cases can be explained by adding a perspective that accounts for flexibility of product configuration, such as customizability. This paper seeks to establish a framework in which to consider competitive strategies for IT products in general by applying methods of analysis developed for PDA market data to other product markets, focusing on what is known as product architecture - that is, how the product is configured and in what combinations the product is used.