I have the T60, and I'm not quite sure what you mean by SD mode. I've just looked at the sound settings for the first time (to answer this post). I'm going to write down what I see on the screen, even though I don't understand it. It has "SRS" settings, in which you can set it on SRS (range is between 1 and 10, factory setting is 6. you can't tell the difference unless you jump from 1 to 10 quickly- 10 is slightly louder and slightly clearer), focus (low, mid, high, factory setting is mid- high is louder and clearer, but the difference is minute on the clearer), trubass (1-10, factory setting 6- even on change between 1 and 10, I can't tell the difference), wow (ranges between 40 and 400, factory setting 40- the higher it goes, the more echoey but louder it seems to be), and definition (factory setting 4, range 1-10- 10 is marginally louder and somewhat clearer than 1).
It also has an equaliser, but it doesn't appear to have "normal, rock, classic, jazz" selections or anything like that.
(Maybe someone who knows more than me can explain what the things on my machine mean- for the OP as well as myself- and whether my observations are correct-ish)