When running AutoCAD 2012 on Windows 7 64-bit, consider the following:
: Portable versions may lack certain shared libraries (like .NET Framework or C++ Redistributables) typically found on a host PC, which can lead to crashes if those dependencies aren't already installed. Legacy Support autocad 2012 portable windows 7 64 bits
Note that Autodesk no longer supports this version for newer operating systems, so keeping it on Windows 7 is your best bet for stability. When running AutoCAD 2012 on Windows 7 64-bit,
System requirements for AutoCAD Architecture 2012 - Autodesk autocad 2012 portable windows 7 64 bits