Digital mock-up (DMU) development plays and important role in the product development processes of the manufacturing industry. Unfortunately most of the DMUs are not created or presented in immersive virtual environments, although the benefits are considerable. The main reasons for it are high hardware costs for immersive environments and lack of specialized tools for designing and manipulating DMUs. Our research efforts address both issues. We developed the ARSBOX, a PC-based flexible and high-performance IVE that can be used for arbitrary display situations. A main distinguishing feature is the possibility to display immersive 3D models together with arbitrary other PC applications (e.g., Microsoft PowerPoint™). Furthermore we developed the Palmist system - a smart combination of a Pocket PC and a software framework that allows to navigate painlessly in immersive 3D worlds and that even allows to change properties of displayed objects and therefore can be used for DMU development.