^ The available Modes are determined by the content you are playing and the number of speakers you have configured.
Press the Select button on the remote several times and note the display that shows the speaker channels coming in on the content you are playing.
If your Dolby Digital input is 5.1, and you have 5.1 speakers configured, there's no work for the Surround Sound Modes to do, so none are offered. (You can still choose to add THX post processing or not with the THX button.)
If you have 7.1 speakers configured, that same 5.1 input will now offer several Mode choices -- i.e., different ways to expand that into 7.1 speakers output.
If you play stereo input, you'll have even more Mode choices available to expand that into 5.1 or 7.1 speakers output.
So what were you playing as input and what were you trying to achieve as output?