I've been meaning to post a warning about this, and when I just checked my email and found 10 of these messages in there, I figured I'd better do it now before I forget. This has been a rather nasty email worm that's been going around for a few weeks, and if I'm getting it, it probably means some of you are sending it to me (not intentionally, of course) Follow the above link for some good information on this thing.
Good rule of thumb: If you get an attachment, and you're NOT 100% sure what it is, DELETE IT. Even if you know the sender. They can always re-send it if it's a valid attachment.