Digital information can be lost for a variety of reasons, including magnetic decay, format and device obsolescence, human or system error, among many others. A solution is to build an archival repository, a system capable of storing and preserving digital objects as technologies and organizations evolve. Designing an archival repository is a complex task because there are many alternative configurations, each with different reliability levels and costs. This paper studies the costs involved in an archival repository and introduces a design framework for evaluating alternatives and choosing the best configuration in terms of reliability and cost. The paper also presents a new version of the simulation tool, ArchSim/C, that aids in the decision process. The design framework and the usage of ArchSim/C are illustrated with a case study of a hypothetical (yet realistic) archival repository shared between two universities. (Contains 12 references.) (Author/AEF)