a newbie:
why do need to make 7-zip installers?

so they're one double click to launch, and don't require switches to run, nice and tidy (one file per program) and are compressed so take up less space on your cd

but how can we silently install them?

7-zip installers are simply repackaged regular installers. The advantage is that the size of the final installer is smaller, meaning that you'll be able to fit more of them onto a CD.

Silent installers are a bit different. They are installers that have all the options entered ahead of time. That way, when you go to run the installer, it simply installs the program with all the options you set, without asking you for input.

To run either, simply double click on the .exe.

Hope that helps.