VB.NET 2005 is not an upgrade from VB6 in any respect. They are two completely different languages and products. VB6 code will not run in VB.NET 2003 or 2005 without some kind of major conversion/rewritting. 2003 and 2005 are all about OOP where VB6 is not.

.NET is, like Hack put it, a 2006 Ferrari Enzio and VB6 is like a 1951 VW Bug with a 1300 cc engine.