Is it the same document? In other words, is the one in the listing the same
one which is in the library? Does it happen with every single presentation
or only specific ones? If it isn't the same one as the one in the library
are you positive that it isn't a .pps? Sometimes, because the name is the
same, you just don't bother to look at the extension (although its kind of
hard to miss on the link and this question is a looong shot).

I just tried to duplicate your error with a variety of PPTs and no matter
what I did or where I looked in settings and options I couldn't duplicate
it...

I thought that how Office documents opened from a Web page was a client
side setting.

When it is at the group  listing or search results, sharepoint  assumes that you are opening  it to view… Hence the activex control installed by office will open  it in powerpoint  viewer… But when you open it in library, sharepoint assumes that you want to edit it, so it opens it in powerpoint itself.. There is no easy way to change this behaviour…

Pretty sure you’re right. All that’s happening from the server  side is the server is streaming down a PPT, and specifying the content type. IE is launching the registered PPT handling app on the client… so I’d assume the client is setup to open  the PPT by default in the manner that was described.

How does SharePoint target the viewer vs. the fat client? Do you know?

I have no idea how it target yet… but I notice that for word, if you click the word link in search result, it is open  within IE, and when you tried to save, the location is in your temp. But if you click it in document library, it opens up in word as a separate window, allowing you to save in doc lib. MCS consultant says somehow the activex control installed when you install office assumes that behaviour…

I don’t see how it could… the only thing it (and it’s not SharePoint, it’s simply a standard HTTP response) is sending down is the data stream and labling what it is with a content type. Unless there are two different types of PPT content types (one for the fat client & one for the viewer), which I would be shocked if there were (that would cause all different kinds of issues as then you’d have to “Save As … PPT for viewer”), I don’t think there’s any way to control what happens on the client… the client makes a determination based on the content type (and what’s in that little “File Types” tab in your folder options).

To continue on. Yes the PPT is stored in the document library, but
it is also added as a portal  listing.

In the library  the file opens in PowerPoint. Through the link it is
opening in the browser as a presentation.

why would a slide deck open  in the fat client from
a WSS list and from the viewer in an SPS Group Listing? Actual document
vs. a link to a document? Permissions?

Maybe the link in a Group Listing is sending the user to a Web page that
only displays documents in their HTML viewer. I am totally speculating
here and I'm also taking at face value that PowerPoint documents do
behave in this way.

That’s the part that’s nagging at me as it surely contradicts what I was thinking.

Maybe the original poster [Moojjoo] could use something like Fiddler to trace the response of both requests… then we can see if it’s actually different (I’m going off the assumption it must be).