For those who still need to run the original AutoCAD 2006 for legacy projects, the legal options are limited. You cannot buy a "new" copy. The only legal way to run it is if you already own a perpetual license from that era.
New capabilities included basic arithmetic expressions (sums and averages) directly within AutoCAD tables. System Requirements (Legacy Check) Autocad 2006 with key full version
Autodesk discontinued support for this version years ago. Conclusion For those who still need to run the