I just noticed that many servers use Microsoft SQL server 2000. But isn't 2000 outdated by 2003? Why are people still using 2000? Would there be any serious security vulnerability by using Microsoft SQL server 2000 sp3a? (MSSQL 8.00.766.00)? What would be the point of running SQL server 2000 in Windows 7 enterprise?
There could be a few factors.
Like ekaj stated, price could be a prohibitive factor as some companies might not be able to afford or justify the cost of upgrading to the newer version, particularly if they do not take security threats seriously.
Another factor could be the need for backward compatibility. I do not have experience with the Microsoft SQL server, so it might not apply in this particular case, but sometimes upgrading software can break compatibility with existing products/solutions. The company in question might not have the people with the right expertise to ensure that the upgrade does not have any compatibility issues.
A quick search of CVE databases turns up a few potential vulnerabilities which may or may not be serious enough to warrant an upgrade.
Some applications will only work in MSSQL 2K - new commands and functions behave differently and can break older applications written on 2K. Even changes in DATE formats can cause problems.