If you ever installed TG3 in the *same directory* as TG2, that was definitely not the right approach. But the defaults are to install *to different directories*. So it already tries to accomplish what you're suggesting, in other words if you accepted the path defaults on the install to begin with, then redoing it won't help. The problem is there are other things besides install path, for example file associations, and environment variables, which can cause problems with multiple installs. We really recommend only have 1 version installed at a time.
If you really want to run multiple versions the best way is to *copy the entire directory contents* of one install (Terragen 2, for example) to a new folder, then *uninstall* the old version, and finally install the new version. The new one (TG3) becomes the default and has file system associations, while you can run the old one just from the copy of the folder, and it should not then have any file system or environment variable associations.
- Oshyan