 <p>Well, when I changed the application pool "Identity" user of my web application from ApplicationPoolIdentity to LocalSystem, it worked. I suppose I could have also changed the user in the service (Control Panel > Services > ANTS Performance Profiler 6 Service) to some other user and used that user.</p> <p><img src="https://i.stack.imgur.com/LXXMd.jpg" alt="enter image description here"></p> <p>But then I get another error. As Kip says in Napolean Dynamite, "I love technology." </p> <p><img src="https://i.stack.imgur.com/cdJUv.jpg" alt="enter image description here"></p> <p><strong>Stack Trace in Details window:</strong></p> <pre><code>Could not start w3wp as the specified user. Win32 error code: 87 RedGate.Profiler.Engine.Startup.IIS.IISException stack trace: at ..StartProfilingIIS(String , String ) at RedGate.Profiler.Engine.Startup.IIS.IISStarter`1.StartProfilingIIS(String currentUserName, String subprocessVariableValue) at System.Runtime.Remoting.Messaging.StackBuilderSink._PrivateProcessMessage(IntPtr md, Object[] args, Object server, Int32 methodPtr, Boolean fExecuteInContext, Object[]&amp; outArgs) at System.Runtime.Remoting.Messaging.StackBuilderSink.SyncProcessMessage(IMessage msg, Int32 methodPtr, Boolean fExecuteInContext) rethrown at [0]: at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg) at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData&amp; msgData, Int32 type) at RedGate.Profiler.Engine.Startup.IIISActuator`1.StartProfilingIIS(String currentUserName, String subprocessVariableValue) </code></pre> <p><strong>After messing around with the error above for a bit, I tried unchecking this option, and it launched my default browser (which appears to be IE 9). Seems to be working now.</strong></p> <p><img src="https://i.stack.imgur.com/kft9N.jpg" alt="enter image description here"></p>