Nb-films (thicknesses of 20 nm, 50 nm and 100 nm), directly grown on orientated Si substrates by DC sputtering, have shown reduced superconducting critical temperatures T-C as compared to the bulk value; an effect associated with their disordered granular character (the disorder phenomenon of the Nb-films depresses the density of states at the Fermi level, consequently shifts the T-C value towards low temperatures). The disorder effect was also correlated to the semiconducting-like behavior observed in the R(T) measurements. At the normal state, while the 100 nm Nb-film is dominated by a metallic-like behavior, the thinner Nb-films (20 nm and 50 nm thick) show significant negative magnetoresistances in a small temperature range about T-C. This behavior was also explained assuming their granular characters, where the applied magnetic field first destroys the global superconducting character of the Nb-films, leaving Cooper pairs localized inside Nb-grains. A further increase of the applied field strength affects the superconductivity inside Nb-grains, enhancing the normal intergranular electric transport channel, which decreases the whole resistance of the Nb-films. The present study suggests that the microscopic disorder, at the grain surfaces/interfaces, seems to be an essential point to comprehend the negative magnetoresistance effect observed in some superconducting granular systems. (C) 2017 Elsevier B.V. All rights reserved.