diff --git a/IPython/utils/_process_cli.py b/IPython/utils/_process_cli.py
index 89a31c3..03b2ecc 100644
--- a/IPython/utils/_process_cli.py
+++ b/IPython/utils/_process_cli.py
@@ -22,14 +22,6 @@ import os
 from IPython.utils import py3compat
 from ._process_common import arg_split
 
-def _find_cmd(cmd):
-    """Find the full path to a command using which."""
-    paths = System.Environment.GetEnvironmentVariable("PATH").Split(os.pathsep)
-    for path in paths:
-        filename = os.path.join(path, cmd)
-        if System.IO.File.Exists(filename):
-            return py3compat.decode(filename)
-    raise OSError("command %r not found" % cmd)
 
 def system(cmd):
     """
diff --git a/IPython/utils/_process_posix.py b/IPython/utils/_process_posix.py
index a9b0e21..5f6b1ab 100644
--- a/IPython/utils/_process_posix.py
+++ b/IPython/utils/_process_posix.py
@@ -31,14 +31,6 @@ from IPython.utils.encoding import DEFAULT_ENCODING
 # Function definitions
 #-----------------------------------------------------------------------------
 
-def _find_cmd(cmd):
-    """Find the full path to a command using which."""
-
-    path = sp.Popen(['/usr/bin/env', 'which', cmd],
-                    stdout=sp.PIPE, stderr=sp.PIPE).communicate()[0]
-    return py3compat.decode(path)
-
-
 class ProcessHandler(object):
     """Execute subprocesses under the control of pexpect.
     """
diff --git a/IPython/utils/_process_win32.py b/IPython/utils/_process_win32.py
index 2f072a8..36fb092 100644
--- a/IPython/utils/_process_win32.py
+++ b/IPython/utils/_process_win32.py
@@ -71,27 +71,6 @@ class AvoidUNCPath(object):
             os.chdir(self.path)
 
 
-def _find_cmd(cmd):
-    """Find the full path to a .bat or .exe using the win32api module."""
-    try:
-        from win32api import SearchPath
-    except ImportError as e:
-        raise ImportError('you need to have pywin32 installed for this to work') from e
-    else:
-        PATH = os.environ['PATH']
-        extensions = ['.exe', '.com', '.bat', '.py']
-        path = None
-        for ext in extensions:
-            try:
-                path = SearchPath(PATH, cmd, ext)[0]
-            except:
-                pass
-        if path is None:
-            raise OSError("command %r not found" % cmd)
-        else:
-            return path
-
-
 def _system_body(p):
     """Callback for _system."""
     enc = DEFAULT_ENCODING