same problem here, too.
yes, I clicked 'windows friendly' and yes, I clicked 'add to end of message'.
I tried sending the message as plain text - the HTM files went away, but were replaced with a blank .txt file.
And sending all my messages in plain text format is not optimal, in my opinion. I guess all my windows-running contacts will have to continue to scratch their heads over these 'extra' attachments.
Anyone have a solution?