“Portable” repacks of older software like AutoCAD 2006 are common vectors for trojans, keyloggers, and ransomware. A paper recommending or detailing their use would be irresponsible from a cybersecurity standpoint.
If you are trying to run AutoCAD 2006 on modern hardware or across multiple machines, here is what you need to know: Official Portability Features AutoCAD 2006 included a built-in Portable License Utility
Exploring AutoCAD 2006 Portable: Legacy Design in a Modern World