Hello ACAD666,
I think the issue you are having is because your installer is 32 bit. AutoCAD does not allow you to install the 32 bit version on a 64 bit OS, only 64bit on 64bit. I would suggest going back to your reseller and get the 64 bit version of 2011.
Hope this helps,
Randall Young
AutoCAD Test Development
Randall Young
Autodesk Lead Engineer
Autodesk, Inc.