Although the emphasis on software usability has grown in the past fifteen years since software designers and developers attempted to incorporate principles of human-computer interaction into their work, some designers have suggested that concerns for usability are not truly integrated into the design and development of educational software (Pavlik, 2000; Levi and Conrad, 2000). To better understand educational software, more usability studies are needed. To address the lack of controlled and situated studies on how the constraints imposed by web-based learning tools affect their usability, we conducted a study to compare two commercially available learning tools. In particular, we wanted to know: