I tried it on two different machines, and got two different answers: conan$ /cygdrive/c/Python25/python -c 'import os.path; print os.path.exists("nul")' False conan$ /cygdrive/c/Python24/python -c 'import os.path; print os.path.exists("nul")' False conan$ /cygdrive/c/Python24/python -c 'import os; print os.stat("nul")' Traceback (most recent call last): File "<string>", line 1, in ? OSError: [Errno 22] Invalid argument: 'nul' conan$ /cygdrive/c/Python25/python -c 'import os; print os.stat("nul")' Traceback (most recent call last): File "<string>", line 1, in <module> WindowsError: [Error 87] The parameter is incorrect: 'nul' titti$ /cygdrive/c/Python24/python -c 'import os.path; print os.path.exists("nul")' True titti$ /cygdrive/c/Python25/python -c 'import os.path; print os.path.exists("nul")' False titti$ /cygdrive/c/Python24/python -c 'import os; print os.stat("nul")' (33206, 0L, 3, 1, 0, 0, 0L, -1, -1, -1) titti$ /cygdrive/c/Python25/python -c 'import os; print os.stat("nul")'Traceback (most recent call last): File "<string>", line 1, in <module> WindowsError: [Error 87] The parameter is incorrect: 'nul' I ran it from a cygwin prompt, but the pythons are native. So you are correct that it doesn't work as I expected in Python 2.4 either on the "conan" host.. On "titti", there is a difference in how os.path.exist works between 2.4 and 2.5. On "conan" there is actually also a difference, but only in the exception raised by os.stat. I don't know what the differences between these installation are.