.att and win.dat attachments aren't real attachments, or if they are the attachments, they've been encoded wrong. Try renaming them to the type of file you think they are, and see if you can open them then.
Outlook has a habit of appending crap to simple messages. As listowner, Outlook Express / Outlook / etc. are the bane of my existence. Why-o-why do these stupid email programs have to include three pages of HTML coding and a bunch of other stuff to a three-text-line message?
It's not SPAM that's filling up / slowing down the Internet, it's Microsoft's bloated communication apps.