Question: I created a setup by Advanced Installer software for my program that I've written by c#. I installed my program on VMWare Windows7.

When I try to run it this message is displayed:

![Class not registered](https://i.stack.imgur.com/efAyh.png)

Answer: 
What if `monthNumber` is not between 1 and 12? In that case, `monthString` won't be initialized. You should give it some default value when you declare it :

```
String monthString = null; // or ""

```
monthString is a local variable within main(), therefore, it must be initialized to prevent the compiler error.

If monthString were a Class variable then it does not have to be initialized explicitly.

You can do this by moving monthString outside of main() and declare it as:

static String monthString;