diff --git a/setup.py b/setup.py
index 0b57cf4af1..1ea2963f12 100644
--- a/setup.py
+++ b/setup.py
@@ -25,12 +25,14 @@
 # Originally by Thomas Heller, started in 2000 or so.
 import glob
 import os
+from collections.abc import Iterable
+from pathlib import Path
 import platform
 import re
 import shutil
 import subprocess
 import sys
-from typing import Union
+from typing import List, Tuple, Union
 import winreg
 
 # setuptools must be imported before distutils for markh in some python versions.
@@ -44,7 +46,6 @@
 from distutils.command.install_data import install_data
 from distutils.command.install_lib import install_lib
 from distutils.core import Extension
-from tempfile import gettempdir
 
 # some modules need a static CRT to avoid problems caused by them having a
 # manifest.
@@ -2123,36 +2124,12 @@ def finalize_options(self):
 swig_include_files = "mapilib adsilib".split()
 
 
-def findall_files(
-    dir: Union[str, os.PathLike],
-    include_pattern: Union[re.Pattern, None] = None,
-    exclude_pattern: Union[re.Pattern, None] = None,
-):
-    """
-    Find all files under 'dir' and return the list of full filenames.
-    Filters by `include_pattern` then excludes `exclude_pattern`
-
-    Re-implemented and simplified from `distutils.filelist.findall`
-    """
-    files = filter(
-        os.path.isfile,
-        (
-            os.path.join(base, file)
-            for base, dirs, files in os.walk(dir, followlinks=True)
-            for file in files
-        ),
-    )
-    if include_pattern:
-        files = filter(include_pattern.search, files)
-    if exclude_pattern:
-        files = filter(lambda file: not exclude_pattern.search(file), files)
-    return files
-
-
-def expand_modules(module_dir: Union[str, os.PathLike[str]]):
+def expand_modules(module_dir: Union[str, os.PathLike]):
     """Helper to allow our script specifications to include wildcards."""
-    files = findall_files(module_dir, include_pattern=re.compile(r"(?s:[^\\]*\.py)\Z"))
-    return [os.path.splitext(name)[0] for name in files]
+    return [
+        str(path.relative_to(module_dir).with_suffix(""))
+        for path in Path(module_dir).rglob("*.py")
+    ]
 
 
 # NOTE: somewhat counter-intuitively, a result list a-la:
@@ -2160,29 +2137,29 @@ def expand_modules(module_dir: Union[str, os.PathLike[str]]):
 # will 'do the right thing' in terms of installing licence.txt into
 # 'Lib/site-packages/pythonwin/licence.txt'.  We exploit this to
 # get 'com/win32com/whatever' installed to 'win32com/whatever'
-def convert_data_files(files):
-    ret = []
+def convert_data_files(files: Iterable[str]):
+    ret: List[Tuple[str, Tuple[str]]] = []
     for file in files:
-        file = os.path.normpath(file)
         if file.find("*") >= 0:
-            files = findall_files(
-                os.path.dirname(file),
-                include_pattern=re.compile(f"(?s:{os.path.basename(file)})\\Z"),
-                # We never want CVS, .pyc and .pyo
-                exclude_pattern=re.compile(r".*\\CVS\\|(?s:[^\\]*\.py[co])\Z)"),
+            files_use = (
+                str(path)
+                for path in Path(file).parent.rglob(os.path.basename(file))
+                if path.suffix not in {".pyc", ".pyo"}
             )
-            if not files:
+            # We never want CVS. This is done in a separate step to have the normalized slashes
+            files_use = [file for file in files_use if not "\\CVS\\" in file]
+            if not files_use:
                 raise RuntimeError("No files match '%s'" % file)
-            files_use = files
         else:
             if not os.path.isfile(file):
                 raise RuntimeError("No file '%s'" % file)
             files_use = (file,)
         for fname in files_use:
             path_use = os.path.dirname(fname)
-            if path_use.startswith("com/") or path_use.startswith("com\\"):
+            if path_use.startswith("com\\"):
                 path_use = path_use[4:]
             ret.append((path_use, (fname,)))
+    print("DEBUG convert_data_files ret:", ret)
     return ret
 
 
@@ -2246,6 +2223,7 @@ def convert_optional_data_files(files):
 ]
 
 py_modules = expand_modules("win32\\lib")
+print("DEBUG py_modules:", py_modules)
 ext_modules = (
     win32_extensions + com_extensions + pythonwin_extensions + other_extensions
 )