On 64-bit machines, support for the 32-bit or 64-bit version of AutoCAD depends on the operating system. For instance, consider a 64-bit machine that lets you boot into either 32-bit or 64-bit Windows. If the machine is running 32-bit Windows, only the 32-bit version of AutoCAD is supported. Conversely, if the machine is running 64-bit Windows, only the 64-bit version of AutoCAD is supported.