In its never-ending attempt to ensure that your projects are not backward compatible, Microsoft's new Visual Basic .NET 2003 upgrades projects from the "classic" VB .NET format. There are a few syntax changes that you may use. For example, the following code declares a For loop variable as it needs it.
For i As Integer = 1 To 10
Aside from that type of change, most VB .NET 2003 code will work in VB .NET. The project solution file, on the other hand, will not. In at least some tests, VB .NET quietly did nothing when I tried to load a VB .NET 2003 solution.
If you try to load a solution in VB .NET and nothing happens, chances are good that it's a VB .NET 2003 solution. To verify that, look at the solution file. In VB .NET the first line looks like this:
Microsoft Visual Studio Solution File, Format Version 7.00
In VB .NET 2003 it looks like this:
Microsoft Visual Studio Solution File, Format Version 8.00
To get the project working in VB .NET, start a new project and copy the .vb files into it. Chances are good it will work.