Add important note for windows services regarding transaction creation

docs/reference/configuration-for-windows-services.md

@@ -9,7 +9,21 @@ applies_to:
     apm_agent_dotnet: ga
 ---
 
-# Configuration for Windows Services [configuration-for-windows-services]
+# Configuration for Windows services [configuration-for-windows-services]
+
+::::{important}
+While the APM agent supports transaction auto-creation for web frameworks such as ASP.NET and ASP.NET Core, it
+doesn't know where the "unit of work" starts for bespoke services. Therefore, it cannot start a transaction
+automatically. As a result, spans, such as those for outbound HTTP requests, are also not captured, as they expect
+a running transaction. Therefore, no trace data will be generated or exported out of the box.
+
+You will need to manually instrument the code for the service to manually create a transaction around the appropriate
+unit of work for your scenario. A custom transaction can be started via the [Public API](/reference/public-api.md).
+
+Alternatively, consider using the [Elastic Distribution of OpenTelemetry for .NET](https://www.elastic.co/docs/reference/opentelemetry/edot-sdks/dotnet)
+where any spans, including those for outbound HTTP requests, are automatically captured. The first span without a
+parent will be considered a transaction when ingested into Elastic Observability.
+::::
 
 Configuration for Windows services can be provided by setting environment variables for the specific Windows service in the Windows registry. With PowerShell
 
@@ -26,10 +40,8 @@ Set-ItemProperty HKLM:SYSTEM\CurrentControlSet\Services\<service-name> -Name Env
 1. define the environment variables to use for the Windows service
 2. `<service-name>` is the name of the Windows service.
 
-
 The service must then be restarted for the change to take effect
 
 ```powershell
 Restart-Service <service-name>
 ```
-