I'm surprised that Windows doesn't protect your first 3 Gigs.
The question was posed to our technical support group as follows: "Can you force ACAD 2009 32 bit to install on a Vista 64 bit machine?" Answer: Installing the 32-bit version of AutoCAD on a 64-bit platform is an unsupported endeavor, and as such we have no documentation for such a procedure. You may, however, find that other users have figured out ways to achieve such an installation. Autodesk discussion forums can be accessed here: http://www.autodesk.com/discussion Should you find a way to install the 32-bit version on a 64-bit platform, it's good to remember that it is an unsupported configuration of the AutoCAD software, and has not been tested by Autodesk.....Autodesk Technical Support
So you were able to install 2009 32 bit into XP mode on a 64 bit machine? Hmmmmm......