We have an AutoCAD plugin that requires 32-bit AutoCAD 2011 (which we have a licence for) and we have a 64-bit OS. I know it's possible to install the 32-bit AutoCAD on Windows 7 64-bit (without using a VM) but I have 2 questions:
1. Is it legal to do so?
2. Where can I obtain the files to skip AutoCADs checking of my 64-bit platform?
When you attempt to install the 32-bit program into your Windows 7 64-bit computer, the AutoCAD installation process will detect your 64-bit OS and will let you know that you cannot run that version of the program on your operating system. To answer your question, it used to be possible to modify the setup files to bypass the OS check, but that is not supported by Autodesk.
As you mentioned the virtual machine route, many versions of Windows 7 do have a free download available from Microsoft called Windows XP Mode, which is a virtual machine with a full installation of 32-bit Windows XP. Into that virtual OS, you can install 32-bit versions of our programs.
With this, you should know that the virtualized video adapter doesn't directly use the hardware acceleration of your system's physical graphics card, so that could affect performance. Also, as with any real 32-bit OS, you'll be limited to a maximum of 4GB RAM usage (total) for the OS, and up to 2GB for each running application (provided that your parent 64-bit OS has that much RAM to allocate to the virtual machine).
To receive the 32-bit AutoCAD 2011 installation files, you may either access your downloads through the Subscription Center if you are using your Previous Version rights, or you can download from the link below. Please note that the link below will expire at the end of the month.