[2003]Why does the .config file vanish ?

I'm working through some exercises regarding the 'TraceSwitch' in the Que 70-306 book, apparently I need to add a xml config file to the bin directory of the project which i've done.
The problem is that the application seems to ignore this file and for some reason it actually vanishes from the bin directory of the project when I run it, anybody got any ideas why this may be happening. ?

VB Code:

The xml file
<?xml version="1.0" encoding="utf-8" ?> 
<configuration>
    <system.diagnostics>
        <switches>
            <add name="FactorialTrace" value="4" />
        </switches>
    </system.diagnostics>
</configuration>

I'm saving this as 'StepByStep12-3.exe.config' in the projects bin folder