The reason you can't open attachments could be because of one liitle setting in Outlook Express... while in OE, go to Tools then Options. From that window select the "Security" tab. Once there, you should see a checkbox with "Do not allow attachments to be saved or opened that could potentially be a virus"? Uncheck it. Then click apply, then Ok.
Restart Outlook Express then try opening your attachment again
Hope This Helps!