Googling around indicates that some people were successful in installing AutoCAD 2000 on Vista by using the Compatibility Mode (use Vista's Help & Support for instructions). However, that was for the 32-bit version of Vista and it appears that AutoCAD 2000 won't run on Vista 64. You can try it and see but you shouldn't be surprised that a 9-year-old program as complicated as AutoCAD won't run on a modern 64-bit operating system.
If you want to look at some of the threads I found, Google using the search term "AutoCAD 2000 on Vista 64".
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