Finding reliable partners for interactions is one of the challenges in ubiquitous computing and P2P systems. We believe, that this problem can be solved by assigning trust values to entities and allowing them to state opinions about the trustworthiness of others. In this paper, we introduce our vision of trust-aided computing, and we present a trust model, called CertainTrust, which can easily be interpreted and adjusted by users and software agents. A key feature of CertainTrust is that it is capable of expressing the certainty of a trust opinion depending on the context of use. We show how trust can be expressed using different representations (one for users and one for software agents) and present an automatic mapping to change between the representations.