error reading files in python 2.5

reports files don't exist under certain conditions

*Doesn't Work Code*
f = open("D:\test.html", "r").read()

*Does Work Code*
(Change file name and retry)

f = open("D:\Test.html", "r").read()

*Comments*
i tried different file types and names all of which made no difference.
When I copied the file (Windows XP) of the file it automatically adds
"Copy of" to the name. I then narrowed it down to the Capital letter in
the name.