My my, so many damn files to choose from for SP1.
Files of interest
The first one contains the whole SP1 she-bang for 32bit, 64bit AMD and 64bit Intel chipsets. It assumes that you're going to be using this DVD multiple times on various machines.
The last 3 are the specific files for each chipset architecture. This saves you from downloading the packs you don't need.
The ones in between aren't terribly useful for the majority of us. It's for people who want to debug the installation process and stuff like that.