When I tried to install Autocad2000 at WindowsXP I got this messase saying that there is a problem installing Autocad 2000 because of my OS (WindowsXP).
So If you Get this error follow these steps:
Go to the Setup.exe (Of Autocad 2000 )file, right click on it and go to Properties. Then click the Compatibility Tab and where it says compatibility mode just click in the box under it and turn it to Windows 2000.
Then click OK and run the Setup.exe
It will work Fine...