This post it for all of you out there (however many of you there may be) who are still running Autodesk products on Windows Vista.
As of January 1, 2012, Autodesk will no longer support Windows Vista for new or upgraded products and services released in 2012.
If Vista was supported for your product when it was released (as it was for AutoCAD LT 2012), that combination will still be supported. But don't count on it for any future products.
Get all the details in the FAQ doc here.