Trying to install ADB USB Drivers, but Nexus is never appearing in Device Manager
You should get the proper USB driver via the SDK Manager (which is the the tool you will run when installing the SDK).

The first step in installing the SDK, is starting the 'SDK Manager", and downloading an Android API package (ie. the code to develop for a specific API)

In the list of options, is an 'Extras' section - that contains the official USB driver for Android developer devices (of which the Nexus S is one).  Download that driver for best results.

You won't need to install the whole SDK using this method, but will need to start down that path, in order to get the proper driver.

Good Luck.