Visual Basic has, until now, carried backward support for QuickBasic-compatible keywords. With Visual Basic. Net, that support goes away, so locate any of the keywords that will become obsolete and remove them from your code. Watch out for variable declarations. In Visual Basic 6, you can declare a variable anywhere in a routine, and it will be available.
Net introduces the concept of block-scope, which changes variable declaration.
The easiest way to grapple with this change is to declare all variables at the top of a routine. Change your form-loading process. In Visual Basic 6, a load is formed by merely referring to it. With Visual Basic. Net, you'll need to declare a form variable, instantiate it, and then show it.