Office doesn't require IIS. It looks like you might be trying to install an office component that is attempting to integrate with the web server. I have no idea what that could be in the core Office product.
Another possibility is that there was already an Office install (or start of one) that is trying to repair itself when you run the new install. This used to happen quite a bit but I haven't seen it in years. It is the self-repair feature of the installer. Historically it was related to a bad COM registration generally.
My first suggestion is to look at the installed products on your machine and remove any Office-related products. There is a lengthy article on StackOverflow that walks through all the things you can do to fix the machine so you can then run the Office installer.