1. How to add an event handler in Visual Studio .NET and in Visual Studio 2005?

To do this we need to use the IEventBindingService and IComponentChangeService of the IDesignerHost of the form.

2. How to override a base class method in Visual Studio .NET and in Visual Studio 2005?

To override a base class method using the Visual Basic Code Editor

Open the form that you want to use in the Code Editor.
From the Class Name drop-down list at the top of the Code Editor, choose (Overrides).

A list of the methods is added to the Event list.
From the Method Name list at the top of the Code Editor, choose the method for which you want to create an event handler.

3. How to get the "old" (version 6) Visual C++ look in the new Visual Studio .NET environment?

I think we cant change the GUI of new version

4. How to run the converter for visual studio IDE?

No idea if you have then share plz

5. How to open only one instance of vb application(.exe)?

Following are the steps to make single instance application
in VB.NET

1.For a Vb.NET project selected in Solution Explorer, click
Properties on the Project menu.

2.Now Click Application tab.

3.Select the Make single instance application check box.