I believe from previous posts that IE cheats on the content type of
downloaded files by looking at the filename as opposed to the content type
spec. To get around it, you have to use the three letter file extension in
the filename that corresponds to your file type (example: .jpg for jpeg
files, .doc for Word docs, .exe for executable files)
--David Smith
And not just the name. Sometimes IE peeks into the file itself, trying to guess what
it is. I believe it happens for unregistered file extensions.
Nix.