I have an all-in-one iso from microsoft on a DVD for Visual Studio Express Basic.NET, C#, C++ and Web developer. If I installed C#, can I also write VB.NET applications on it, or do I have to install all four programs?
When you install VS Studio Express, by default it installs templates for Visual Basic, C# and C++. If you want to work with VB.Net, the template for that is available on-line.
There aren't individual programs to install, there's one program and it supports a myriad of templates.
Seems to me that since you have the DVD why not just install it and see for yourself?