... so to be more specific:

For a picture that is not doing what you want, go to the Event Pan/Crop window.
Right click anywhere on the picture.
Choose "Match Source Aspect"
If necessary, resize using the handles on the edge of the frame until the entire picture shows.

Is there a way to have this as a default setting? Ideally, I'd like to avoid going through that process for each photo in the slideshow.

So odd. In *every* version of Vegas i've used (10 of them so far) that has been the default. Vegas has always automatically matched the source ratio. Lots of folks would like to have what's happening to you be the default instead.

That's weird. I wonder what function or control I accidentally changed?

Every photo I put into VMS 6 takes up the full screen when the DVD is played, meaning that the edges of the picture are not seen. Kinda like watching a pan & scan movie on network TV.

I've tried clicking the match aspects control, but it still comes out this way. I've have to dig into this more. Thanks again.

Ohhhhhhhhhhhhhhhhhhhh!!!! Now i see what's going on.

This has nothing to do with aspect ratios. What you're encountering is overscan. Almost all televisions cut off some of the edges of the frame. This is done for a variety of historical reasons, few of which matter much today, but we're still stuck with it.

The absolute best way to deal with it is keep it in mind when shooting the pictures to begin with and make sure that you include extra space around your subjects when framing them before clicking the shutter release.

The next best way to deal with it is to just accept it and let it be. All TVs overscan by a different amount, some of the newer ones overscan very little. Your computer monitor probably doesn't overscan at all. So if you try to adjust for it on some monitors you may end up having extra space around the image that looks ugly on other monitors.

The third way to deal with it is to use Pan/Crop to drag the cropping rectangle out larger than the image, which thereby shrinks the image in the frame. There's no set way to do this though, because all monitors cut off a different amount. If you shrink it enough to look good on your TV, it may still be too large for others, and small enough to leave a large black border around it on other TVs.

So, a hybrid approach is to shrink the pictures enough, then on a lower track put some bland or complimentary background to fill the frame behind the image. This way those with less overscan on their monitors will see something pretty instead of the ugly black border.