simple message lib not found

Using Arduino Programming Questions
6

Would you bother to explain how this should look like ?

Well, I think it's pretty obvious what this means:

#if defined(ARDUINO) && ARDUINO >= 100

I think it's pretty obvious what this means:

#else

I don't think it takes much imagination to determine under what circumstances the SimpleMessageSystem header file gets included and under what circumstances it does not.

If you agree that it is being included only under certain circumstances, and that those are not the correct circumstances, then you should feel free to move the include statement.

I am using the "SimpleMessageSystem Example 1"

That example is included with a library that you have not explained where you got it. That leaves you as the only one that knows what your code looks like.