The easiest way to learn SQL Server is to grab a book on T/SQL that you find easy to read and start using it. Without using it hands on it will be very hard to pick up.
You might want to start with SQL Server 2005. SQL Server 2000 is an older product, which while still widely in use has been replaced by SQL Server 2005, and SQL Server 2008 is coming out in a few months (Q3 or Q4 2008).
Knowing more about what you want to do with SQL Server, either database development or database administration will help people provide advise easier.