The single-electron capture process in the collision of fast protons with ground-state hydrogen molecules has been studied assuming an effective one-electron model. A Hartree-Fock molecular wavefunction, within a first-order Born approximation with correct boundary conditions, is employed to evaluate the transition amplitude. The dependence of the differential capture cross sections on the molecular orientation is examined. The oscillation of the cross sections, due to the interference between the scattering from two molecular nuclei, is investigated. Integrated cross sections are calculated and the results have been compared with available experimental data as well as other theoretical calculations.