The New Xbox Experience was released today and one of the new features allows you to install your games to the HDD. While you still have to keep the original disc in the tray, installing to the HDD can make some games perform a little better while also putting a little less wear-and-tear on your DVD drive.
However, this isn't to say that ALL games will see optimizations from being installed. In fact, in the case of Halo 3, the game will actually see increased loading times. Several websites have reported the results of tests to gauge how some games perform after being installed to the HDD for Halo 3 and their tests indicate that in some cases, the load times are significantly longer.
Halo 3's Developer, Bungie, conducted their own internal investigations and confirmed these observations.
To speed up loading times, Halo 3 caches the data from the DVD unto the Hard Disk. If you try to launch the game from the Hard Disk, it will do the same and try to cache the data from the Hard Disk and unto itself. Unlike when copying from a separate drive, data cannot be read and written on the Hard Disk simultaneously.
In the mean time, Bungie advises against installing Halo 3 on you Xbox 360 Hard Disk, and they promise no patches to fix the problem. "While anything is possible, it would be a significant undertaking to try and retroactively patch/update Halo 3 to be optimized to take advantage of the HDD install features of NXE," they wrote on their official site. "The risks of doing that and the resources required has to be carefully considered against what could really be a rather insignificant change to the player experience. For now our team is focused on making great games for the future like Halo 3 : Recon and other unannounced projects but we will continue to monitor this situation."