This paper examines undergraduate student use of laptop computers during a lecture-style class that includes substantial problem-solving activities and graphic-based content. The study includes both a self-reported use component collected from student surveys as well as a monitored use component collected via activity monitoring "spyware" installed on student laptops. We categorize multitasking activities into "productive" (course-related) versus "distractive" (non course-related) tasks. Quantifiable measures of software multitasking behavior are introduced to measure the "frequency" of student multitasking, the "duration" of student multitasking, and the "extent" to which students engage in distractive versus productive tasks. We find that students engage in substantial multitasking behavior with their laptops and have non course-related software applications open and active about 42% of the time. There is a statistically significant inverse relationship between the ratio of distractive versus productive multitasking behavior during lectures and academic performance. We also observe that students understate the frequency of email and instant messaging (IM) use in the classroom when self-reporting on their laptop usage. (Contains 9 tables and 5 endnotes.)