Ballistic electron magnetic microscopy is used to study spin-dependent hot-electron transport and local magnetic switching of ferromagnetic thin films grown on a Au/Si(100) collector. For Ni80Fe20 films, the collector current is a factor of 2 larger than for Co, consistent with the shorter hot-electron attenuation length of Co. For Ni80Fe20/Au/Co spin valves, the collector current is reduced by a factor of 5 when the relative magnetization of the ferromagnetic layers changes from parallel to antiparallel. By sweeping the applied magnetic field, we obtain nanoscale hysteresis loops, where the hot electrons are collected from an area of about 10 nm.