Variable or constant. Eh?

not being totally up on all things pc-wise, i’ve just downloaded the latest version of DVD21, and have no idea what the “variable/constant” option does for me. what is it, when should i use it and why? any help would be warmly recieved. oh, and while i’m on, is it safe for me to just delete the previous versions of DVD21 from my HD?

Read the rest of the forum, this is being discussed on several occasions!