It's not uncommon to want to install Apple's component software, separate to iTunes itself, especially if you're using a third-party music manager. But what if you just want iTunes? Well, if you do it's quite safe to remove everything else that comes with the app, leaving you with the player only.
Depending on whether or not you have iTunes installed already, you have two options:
1. Clean out the installer file before running it
If you've yet to run the installer from Apple's website, you can crack open the file with an archiver utility such as 7-Zip and simply extract the components you want. In this case, if you want iTunes alone, grab the "iTunes64.msi" file and run it.
Unfortunately, you still have to download the entire file to begin with, so it won't save you any bandwidth. But it does simplify things.
2. Uninstall the unwanted components
iTunes already installed? No problem. Luckily for us, Apple doesn't tie all the components together — you can uninstall the parts you don't want via Windows' Programs and Features dialog.
Keep in mind that if you do need to plug in your iPhone or other iOS device, removing these will almost certainly stop that from working.
If in doubt, Martin Brinkmann over at gHacks has a breakdown of each component, so you can decide what's safe to remove.