Throughout the 1970s and 1980s, computers in science teaching were seen as a panacea for many problems plaguing the domain. While considerable research has been done to determine cognitive achievements of students who interact with computers during their science learning, more basic questions have not yet been addressed. This study was designed to investigate how computers and a modeling software contributed to students' interactions and learning in a physics course. The interpretations focused on the microworld as a tool that supported but also limited students' sense-making activities. First, the computer microworld contributed in significant ways to the maintenance and coordination of students' physics conversations. Second, the computer environment (a) was sometimes "unready to hand" so that students spent more time learning the software rather than physics, and (b) limited the interactions within groups. It was concluded that while computer environments have some potential as learning tools, they also limit interactions in significant ways, rendering them less than ideal for everyday classroom use.