Slideshow in Outllook turns screensaver

We have had a problem with running a Powerpoint 2000 Slideshow (pps) file from Outlook. When you double-click on the slideshow attachment from an Outlook message, it runs the slideshow correctly, but then the screensaver automatically sets itself back to none. Microsoft’s fix for this is to run SP2. We cannot install SP2; it will limit the file type attachments permitted through Outlook.