Microsoft will be turning off mainstream support for SQL server 2000 for most editions of the product in April 2008:
General Availability Date
Mainstream Support Retired
Extended Support Retired
SQL Server 2000 64-bit Edition
SQL Server 2000 Developer Edition
SQL Server 2000 Enterprise Edition
SQL Server 2000 Standard Edition
SQL Server 2000 Windows CE Edition 2.0
SQL Server 2000 Workgroup Edition
Details can be found here
That isn't very far away considering the work needed to test and migrate applications, and I know that some organisations aren't even aware that they may have some of these database lying around.
However if we forget the imperative that this deadline means to those who only want to have supported products in their infrastructure then there are loads of reasons for moving away from SQL server 2000. For me security would have to figure high on this list as SQL server was designed in an age where always on Internet connections were not prevalent as they are today. I wonder how many installations are still out there with no password for sa waiting for a little bit of SQL injection?
Of course SQL server 2000 can be locked down and applying all the patches and fixes is also essential but SQL server 2005 is secure by design and by deployment i.e. out of the box.
Cost is usually mentioned as the main reason for not upgrading, the majority of which is the work involved rather than any license costs. I would say that this is a lot easier now if only because any problem you might encounter has almost certainly been resolved elsewhere by other IT Professionals and this information is widely available not just on the TechNet SQL Server TechCenter SQL but on the SQL community site and in the numerous publications out there.
As ever I'm happy to dive into this in more detail if it's useful.
My first ever blog post was about the features of SQL Server 2000 that won’t work in SQL Server 2008,