Everything points to the fact that .dw2 and .dc files are used in DesignCAD and both might very well be CAD design files, so it is fair to assume that some kind of dw2 to dc conversion is doable.
We have not found any 3rd party software that would support DesignCAD formats, so using the origina software is most likely your only option here. If you have some other issues with export of either of these file types, it might be best to reach out to IMSI Design support.