Index: Lib/subprocess.py
===================================================================
--- Lib/subprocess.py	2009-09-29 21:18:11.000000000 +0200
+++ Lib/subprocess.py	2009-10-15 16:40:11.000000000 +0200
@@ -934,7 +934,10 @@
         def terminate(self):
             """Terminates the process
             """
-            TerminateProcess(self._handle, 1)
+            if self.poll() is None:
+                TerminateProcess(self._handle, 1)
+            else:
+                raise OSError("Child %d has already terminated." %self.pid)
 
         kill = terminate
 
@@ -1232,11 +1235,14 @@
 
             self.wait()
             return (stdout, stderr)
-
+            
         def send_signal(self, sig):
             """Send a signal to the process
             """
-            os.kill(self.pid, sig)
+            if self.poll() is None:
+                os.kill(self.pid, sig)
+            else:
+                raise OSError("Child %d has already terminated." %self.pid)
 
         def terminate(self):
             """Terminate the process with SIGTERM