title: Exception: Instance 'Name of instance' does not exist in the specified Category
body: <p>When I create and use performance counters like this:</p>
  
  <pre><code>private readonly PerformanceCounter _cpuPerformanceCounter;
  public ProcessViewModel(Process process)
          {
  
               _cpuPerformanceCounter = new PerformanceCounter("Process", "% Processor Time", process.ProcessName, true);
          }
  
  public void Update()
          {
              CPU = (int)_cpuPerformanceCounter.NextValue() / Environment.ProcessorCount; // Exception
          }
  </code></pre>
  
  <p>... I get an exception <strong>Instance 'Name of instance' does not exist in the specified Category</strong> and don't understand why.</p>
  
  <p>P.S. Code</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8" ?&gt;
  &lt;configuration&gt;
    &lt;system.net&gt;
      &lt;settings&gt;
        &lt;performanceCounters enabled="true"/&gt;
      &lt;/settings&gt;
    &lt;/system.net&gt;
  &lt;/configuration&gt;
  </code></pre>
  
  <p>... included in App.config.</p>