I'm struggling to understand how can I change the garbage collector mode on .NET 4.0 from Workstation to Concurrent mode. I've found out I need to add these lines to some config file:

```
<configuration>
   <runtime>
      <gcConcurrent enabled="true"/>
   </runtime>
</configuration>

```

However, I'm not sure what configuration file they mean here. Nevertheless, I went to the **machine.config** under C:\Windows\Microsoft.NET\Framework\v4.0.30319\Config hoping that this was a machine-wide setting and still that didn't help. I noticed my dlls also had their own config files, but updating those also didn't help. 
Note that my application doesn't have an app.config. 

Later on I've run a test dll in nunit, where I also wanted to set the GC mode to Concurrent. So I thought I should configure nunit: **nunit-x86.exe.config** under C:\Program Files (x86)\NUnit 2.6.2\bin. This also didn't have any effect.

Any clues ? Which config file should I update ?

Thanks,
Greetings,
 Sorin