Have you tried associating TurboCad with .tcw files yourself?
Click the windows icon (bottom left corner) and choose the settings cogwheel.
Click Apps, then select Default Apps, then click Choose default apps by file type.
The next window takes a while to populate, but when it does, scroll down until you find the ,tcw entry.
You should then be able to choose Tcad as the app to open such files.
TC21.2 x64 Plat, Bld59
TC16.2 Plat, Bld54.0