I purchased AutoCad 2006 but it doesn't work in W. Vista so Can I do something to make it working?

Open up c:\ -> Program Files -> AutoCAD 2006, then right-click on acad.exe, choose properties, open up Compatibility tab, click the on near the bottom labeled "Show Settings for All Users", accept UAC, check box labeled "Run this program as an Administrator", click OK, check box again labeled "Run this program as an Administrator", click OK and close explorer.