Hierarchies have long been used as useful structuring mechanisms for organizing and managing documents. This study looks at the problem of personal digital document management in the context of knowledge workers. We study and document strategies that users employ to manage the complexity imposed by the volume and variety of personal digital documents. Exploratory research was conducted, analyzing the file systems of 73 knowledge workers using Microsoft Windows in a university setting. The empirical results of this are presented, and compared to a previous study that examined the file systems of 11 users.