I don't know the answer for certain, but the vast majority of software packages put their license files and preference files in the following places:
/Users/<your username>/Library/Application Support
Look inside those directories for files or folders related to IMSI or to TurboCAD. Another possibility is that TurboCAD might use flexLM or some other license manager, too, so you might want to investigate that, just in case.
More rarely, the license is stored within the Application folder itself. (In Mac OS X, most applications are actually special kinds of directories that contain binaries and support files, but they behave like apps hen you double click on them. To see the contents of those special directories, control-click on the app and select "Show Package Contents", or just use the old UNIX "ls" comand on the command line.)
Have you tried asking the question in the TurboCAD Mac support forum? http://tcmacforum.imsisupport.com/index.php
Unless you are certain that your hard drive problem is a software problem and not a hardware problem, I'd give strong consideration to replacing the drive entirely. It can be a bit of a chore to open up modern iMacs
, so you might want to take it to a repair shop or just use an external drive. If you do decide to try reformatting, try reformatting it using Disk Utility's Secure Erase / Seven Pass option. It takes a long time (hours), but by attempting to write zeros to every block on the disk seven times, it does a really good job of identifying drives with hardware problems.
In any case, with external hard drives so cheap these days, you should definitely try to backup/clone the existing drive before you erase it.
One final note: I have pretty much every hard drive repair program in my toolbox. For serious problems, I've found that nothing beats the combination of Prosoft Engineering's Drive Genius and Data Rescue
programs. The latter in particular has rescued files from totally fubarred drives that other software packages wouldn't even mount. (Disclaimer: I have no connection with Prosoft, aside from the fact that their products have saved my bacon a couple of times.)