If you are trying to run AutoCAD 2007 on Windows Vista then listen up. We have been asked this question more times in the past several months than any other-- "How can I get it to work on Vista?"
Autodesk has released SP2 for AutoCAD 2007. Here is the link to download SP2. The only hiccup in the service patch is if you have already installed SP1. Due to a limitation in Service Pack 1, Service Pack 2 cannot be installed on Windows Vista with SP1 already installed. To install SP2, first uninstall and reinstall AutoCAD and then apply SP2 (without installing SP1.)