FastCAD supports natively export to DXF or DWF, so you can use to for FCW to DWG conversion. There is a 14-days trial version available on the developers website, so that should be more than enough for you to perform the conversion.
Convert FastCAD CAD file to AutoCAD drawing.
We found one software available in the database for this conversion.
Microsoft Windows software - convert fcw to dwg on Windows
A high-precision professional 2d/3d CAD System
Convert from fcw file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.