You have a number of choices which can make things confusing.

First does your TV/monitor have a DVI or HDMI input? If it has a DVI input then for video you could run a HDMI to DVI cable from the Toshiba to the 990 and run a DVI cable to your TV from the 990. That takes care of your video feed. You would still need to run one of the audio options such as optical or digital cable.

EDIT: After seeing cappra's post I would say if you are using the HDMI/DVI route for your video to run your audio with the 5.1 analog connections. It seems that way you get the intended HD multi-channel sound.

If your TV doesn't have a DVI or HDMI input you would connect your video via the component connections and then decide on an audio connection.

I have to admit I am not completely up to speed regarding the HD DVD player. I'm pretty sure you don't need to be concerned with the 5.1 analog outputs to get multi-channel sound with an HD DVD. I use the 5.1 channel on the 990 for my SACD/DVD audio player. There is currently nothing with a 7.1 analog output, Outlaw included that with an eye to the future.

Hope this helps some. My ability to explain things in writing is not always that comprehesible.