The documentation for os.path.normcase reads the case gets normalized
based on the file system
http://docs.python.org/dev/library/os.path.html

Current documentation:
Normalize the case of a pathname. On Unix, this returns the path
unchanged; on case-insensitive filesystems, it converts the path to
lowercase. On Windows, it also converts forward slashes to backward slashes.

Problem:
When mounting a network drive (via Samba) onto windows the mapped
network drive will claim to be an NTFS network (on Windows XP). Where
the network drive is actually a Samba share this can cause problems with
case sensitivity versus case insensitivity.

More:
The Windows based file systems such as FAT, FAT32 and NTFS are as a
matter of fact case preservant but case insensitive. That is a file
saved with the name 'MyName' will retain its name as 'MyName' and a ls
(dir) command will returnr the file as 'MyName' however access to
'Myname' or 'myname' or 'MYNAME' will all still access the same file.

Solution:
I suggest we drop converting the case to lower case where the file
systems FAT, FAT32 and NTFS are involved