NAV 2009 Classic & Windows 2000
Since a while Windows 2000 was no longer supported with Dynamics NAV as you can read on Kriki's blog.
http://mibuso.com/blogs/kriki/2010/03/17/happy-birthdayretirement-windows-2000/
But as many of you also know, in version 5 is was only the installer that returned an error message. It was still possible to copy and paste the binaries and start the client.
In 2009 you will get the same error with the installer, but when trying to start the copy/pasted client you will receive this error message: (Sorry Dutch)
For me that means that NAV 2009 is really no longer working on Windows 2000. We installed all updates but that did not help.
So, if you are planning an upgrade: make an inventory of you systems first and be careful not to miss the 'invisible' interface machines. 