Curious, why exactly the Witcher 2 install files for windows are .bins? Why is there not a compiled .exe file for manual installs?

When you download all the parts there should be a bunch of .bin files with an .exe. You don't have to do anything with the .bins yourself, because the .exe does everything. I assume they cut the bigger files into smaller pieces to avoid stuff like:

"The download is corrupted! I have to download the whole thing over again? This site sucks!"

"What do you mean this won't fit onto my FAT32 thumb drive/external hard drive? This site sucks!"

.bin-s are there to cut down individual download, so that when your internet has problems, you don't have to download 20gb all over again. The .exe uses the .bins to install the game, so you need to download them all (if you are downloading manually, when you use the downloader, then it downloads them all automagically)

There is; one of the files is a .exe If you didn't get the .exe, you didn't get a correct download.

Once you have the .exe and all the .bin files in one place, launch the .exe, and it will unpack the .bin files.