Many commonly used PC-based data acquisition counter boards are specified to countregularly occurringevents at rates up to 7 MHz. Boards with this frequency limit begin to systematically and significantly underestimate the rate ofrandomly occurringevents occurring at average frequencies much lower than the specified 7 MHz rate due to the dead time of the counter. This report highlights the origin of this error and describes an easily constructed prescaler circuit that permits accurate event counting at rates up to, and even exceeding, the nominal speed of the counter. ©1998 American Institute of Physics.