I have a very simple and effective approach, my runtime is always below 2GB that is the size of driver E:.
I don't use all what I have, I keep only in disk what I use. Time to time I add something new and what is obsolete or don't use it anymore goes to a CD, I have more than a hundred of CDs (zipped).
Is very easy to administrate 2GB and a full backup of my actual Poser fits in only two zipped CDs (in one all the textures and in the other all the runtime).
If very good to have a small partition, when you have no space to put something new it means that you have a lot of obsolete things to saved for making room for the new.

Stupidity also evolves!