If you don't have the space, either install one disc at a time or just play from the disc with no install at all. It's not that big of a deal. Installs are not mandatory on the 360. It just improves loading speed (in some games), reduces system noise, and reduces wear and tear on the DVD drive. There is NO downside to 360 installs in any game (except Halo 3). It's a nice OPTIONAL bonus feature for those with a little extra HDD space.