Because the demand for OS is a derived demand revealed through the demand for PCs and because its elasticity is relatively small, the profit-maximizing price of DOS/WIN that would result from a static equilibrium is much higher than the observed price. We investigate this assertion empirically by fitting a differentiated-products model of the home PC market to panel data of all PC brands sold in the G7 countries over the period 1995–1999. The results confirm that the low value of the aggregate elasticity of demand for PCs is the result of differentiation and substitution among PCs.