Outlook Express--Attachments that won't open.

I have both Outlook Express and Microsoft Outlook 2003 on my computer.  Each one has one email address on it.  Both addresses receive many of the same emails.  When I receive emails on Outlook Express with attachments that should open with Power Point Viewer, I can't open them.  I get an error message that says "This file does not have a program associated with it for performing this action."

However, when I open the very same email and its pps attachment in Microsoft Outlook, the attachment opens with no difficulty.  And I have gone into Control Panel/Folder Options and found Power Point Viewer as the recommended program.

Now, one answer is obvious:  If I can't open a particular email in Outlook Express, and I have the same email in MO, open it in MO.

That's fine when the email shows up at both addresses.  But when it shows up only in Outlook Express, how can I get it to open?

Thanks for your time. . .

Squirrelly