The specified service has been marked for deletion error message when removing a service

If you receive this message while trying to delete a windows service - check if the Services.msc application is open.

You will need to restart in order to delete the service, but you will know to first close the Services.msc application the next time PRIOR uninstalling the service (using installutil /u service_exe_name).

Hope this helps someone outthere...

Edit : I found another scenario when this can happen and it seems to be more .NET specific and common to software developers - if your service creates some worker threads, Windows will attempt to kill the main thread, the main thread will attempt to kill the main thread but the worker threads if not marked as BackgroundThreads via the IsBackgroundThread property will remain. The GC will wait for them to reach a safe point so they can be terminated and the service will most probably be only marked for deletion, requiring you to restart windows.

Please note - if you are using the ThreadPool class you will probably not hit this problem as the ThreadPool internal threads are automatically marked as background threads.

Edit 2: Another case when you will receive The specified service has been marked for deletion error message is when you try to uninstall service which wasn't stopped first or it was marked as unstopable.
This is done if you have this.CanStop = false in your service code.
Windows knows this service shouldn't be stopped and it will only mark it for deletion but will not delete it right away.
Be careful with CanStop property.