#Use halo 2 product key without disk install
It does have an option to do the full install the usual way. When you are done, you will need to open regedit and delete the registry key you imported before you started playing (if you forget where to find it, look at the paths back in the first section). Basically, what theyre doing is making the game install itself (with a visible on the main menu) as you play. (If this isn't installed already, you will have issues with the chat UI disappearing). Install redist\msxmlenu.msi from the Halo directory. 2.) Then install Halo 2 (it will take a little bit, just so you know) Do not try to install the game without the Games for Windows Marketplace client.reg file, change the EXE Path value to the proper USB path (this may change depending on what drive letter you get when you plug in in, hence the need to change it). This will be the one with Wow6432Node for 64-bit systems, and without it for 32-bit systems.
Now, when you want to play, you will need to do the following. Make a copy of it, and remove or add the Wow6432Node in this copy so that you have one of each.