It's available in all newer incarnations of Photoshop since I made this tutorial. (And there is no Such thing as Adobe 8.0. They stopped at the 7 series and all versions afterwards have been CS#). I'm using CS5 now and still use the same method to isolate linework via channel selection.
Oh, i didn't realise it was referred to as CS, thanks I don't know where it is then... i've searched for it in help, and looked on google to see if the version i have has a channels option, and can't find anything... Maybe it's just me.