The term "install base" is a term used to describe the number of a given product in the hands of users -- generally technical products in nature. If they used "installed base", they mean in users hands -- not in stores. Simple as that.
Keep in mind that MS pays a royal sum for NPD analysis and I'm sure they get data from Europe and Asia as well. They, more than anyone, would have the closest "install base" number. Factor in that they KNOW for certain how many they have manufactured and can get a pretty darn close idea as to how many are in the channel, they will certainly be able to glean a pretty darn accurate install base number.
I hate trolls.
Systems I currently own: 360, PS3, Wii, DS Lite (2)
Systems I've owned: PS2, PS1, Dreamcast, Saturn, 3DO, Genesis, Gamecube, N64, SNES, NES, GBA, GB, C64, Amiga, Atari 2600 and 5200, Sega Game Gear, Vectrex, Intellivision, Pong. Yes, Pong.
