Which operating system do you use? You can open old file types in the newest Archicad. I believe Archicad 25 will open any file all the way back to Archicad 10 you just need to make sure to load the migration libraries too. Older versions of Archicad will unlikely function properly on more modern operating systems.
Lee Hankins ArchiCAD 4.5 - Archicad 27UKI Apple Silicon 5003 macOS Ventura (13.5.2)