If you mean by default you have the menu option selected to Stereo, you may want to change that to DD or DD+PLIIx, this assuming you want to watch your movies in surround sound. You also need to use the optical or coax selection for this to work and what I found is that I got more menu selection options if the source was active. i.e. for my cable box, if I was toggling the default surround format while on a non-5.1 enabled feed, the options did not allow for me to choose DD+PLIIx.

If your using your DVD for both movies and CD's, then I suggest you run the output use the CD input for the default to Stereo option and thus use the CD for playing music, then switching to the video for playing movies and your defaults will be different for each. This is what I do as I have my DVD Player driving three source inputs in the 990, DVD, CD, and 7.1 direct, each with their own default settings.