"Portable" versions of AutoCAD 2005 found on third-party sites are usually unauthorized "repacks" created using virtualization tools like VMware ThinApp or Spoon. These versions are designed to run directly from a USB drive or local folder without writing significant data to the Windows registry. Why Users Seek the 2005 Version

Technically, Autodesk never released an official "portable" version of AutoCAD 2005. Most versions found online are unofficial "thin-app" or "sandboxed" versions. The "Retro" Appeal

: These versions claim to run without installation, bypassing the registry and leaving no footprint on the host computer. The Risks of Using Portable/Unofficial Versions