I had wanted to leave it installed, so that I could show my friends when they visit. A lot of them picked up Portal when it was free, and I'm trying to convince everyone who did so to play TFV as well (it's the only mappack I recommend). This is why I'm trying to get it running on OSX (my media computer, in the living room on the big TV) when it would be easier to get it running on Windows (my bedroom computer) [although, THAT computer DOES have HL2 installed already].
I don't need to play TFV for myself, I already did that a long long time ago. It was excellent, which is why I want everyone to see it.
How about this: I know when a Source game is installed, there are a bunch of gigantic resource files. Is there one in particular that has the stuff that TFV needs? Because, I can just leave that in there when I uninstall the rest of HL2. I don't need to know the actual resources involved, I just want the 50 meg add-on to not turn into a 5 gig exercise.