A numerical study of the forced and mixed convective cooling of heat dissipating electronic components, located in a rectangular enclosure, and cooled by an external through-flow of air is carried out. A conjugate problem is solved, describing the flow and thermal fields in air, as well as the thermal field within the walls of the enclosure and the electronic components themselves. The interaction between the components is of interest here, depending on their relative placement in the enclosure and different configurations are considered. Laminar, steady flow is predicted for up to Gr/Re2 = 10, but a single-frequency oscillatory behavior is observed for most of the configurations studied, at Gr/Re2 = 50. Heat transfer results are presented for both the laminar and the oscillatory domains. The mixed convection regime, where the buoyancy effects are comparable to the forced flow, occurs at values of Gr/Re2 between 0.01 and 10. The results are of value in the search for a suitable placement of electronic components in an enclosed region for an effective heat removal.