OK. Try deleting the service using the sc delete command
http://blog.shawnhyde.com/post/2008/07/04/How-to-remove-a-Service-from-Windows-Server-2008-2008-R2-or-Windows-Vista-7.aspx to see whether it is the service that is the problem.
Now start the application server manually using startServer.bat from it's profile bin directory making sure the startNode.bat is called first and the node agent is running and synchronised.
Then try adding it again by navigating to the apps servers profile bin d:\IBM\WebSphere\AppServer\profiles\STPROXYPROFILS\bin in a command prompt run wasservicehelper.bat and follow the instructions for creating a new service.
Once the service is started stop the apps server and node agent from the ISC or using stopServer.bat and start it from the Windoze service.