We are still using Enterprise Instrumentation(that was created during .Net 1.1 time)In new Server 2008 environment and IIS 7 we have the following errors:The 'sessionName' parameter of value 'TraceSession' is not valid. A trace session of this name does not exist in the TraceSessions configuration file for Windows Trace Session Manager service. Ensure that a session of this name exists in the TraceSessions configuration file and that the Windows Trace Session Manager service is started. at Microsoft.EnterpriseInstrumentation.EventSinks.TraceEventSink..ctor(IDictionary parameters, EventSource eventSource) --- End of inner exception stack trace --- at System.RuntimeMethodHandle._InvokeConstructor(IRuntimeMethodInfo method, Object[] args, SignatureStruct& signature, RuntimeType declaringType) at System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes) at Microsoft.EnterpriseInstrumentation.EventSinks.EventSink.CreateNewEventSinks(DataRow[] eventSinkRows, EventSource eventSource)I’ve seen the same errors on development Win7 machines when using IIS. It seems not a problem on Cassini.I've checked ,that Windows Trace Session Manager Service has started and The file C:\Program Files (x86)\Microsoft Enterprise Instrumentation\Bin\Trace Service\TraceSessions.config has corresponding entry<?xml version="1.0" encoding="utf-8" ?><configuration > <defaultParameters minBuffers="4" maxFileSize="10" maxBuffers="25" bufferSize="20" logFileMode="sequential" flushTimer="3" /> <sessionList> <session name="TraceSession" enabled="false" fileName="C:\Program Files (x86)\Microsoft Enterprise Instrumentation\Bin\Trace Service\Logs\TraceLog.log" /> </sessionList></configuration>The errors still continue, but I was able to disable the parameter in eventSink configuration <eventSink name=" traceSink" description=" Outputs events to the Windows Event Trace." type ="Microsoft.EnterpriseInstrumentation.EventSinks.TraceEventSink "> <!-- MNF disabled parameter to avoid error "The 'sessionName' parameter of value 'TraceSession' is not valid" < parameter name ="sessionName " value ="TraceSession " /> --> </ eventSink>Related old post http://bytes.com/topic/net/answers/104761-enterprise-instrumentation-windows-trace-session-managerOne day I wish to replace all EnterpriseInstrumentation calls with NLog.