In this note a novel, very low-cost alpha-particle spectrometer has been described. The spectrometer's design is based on the concept of virtual instrumentation. It consists of a self-contained alpha probe connected to a PC through the USB bus and of PC application software. The probe uses a new arrangement of a large-area standard PIN photodiode and commercial off-the-shelf electronic components. The spectrometer has an energy resolution of 56 keV (239Pu) and a throughput of 103 cps. Due to its low-power consumption—not exceeding 200 mW—it can be used with laptop or palmtop computers as a portable spectrometer for field measurements.