It depends on how much you "used" it. An experienced developer should not have a problem updating his knowledge of changes in 3.0 and 3.5 Framework and changes specific to a language. The biggest introduction, I would say, has since been LINQ, making it possible to query data from the language level, not SQL.
But if you are not an experience developer and do not have a good foundation in the previous version, most of what you will learn will be Framework 3.0 and VS2005.
, , VS2005 2008 , .