Google Nexus S USB Drivers for Windows 7 64Bit
The USB Driver for Windows is available for download as an optional SDK component. You need the driver only if you are developing on Windows and want to connect an Android-powered device (ADP, Nexus One, or Nexus S) to your development environment over USB.

Are you going to develop android app or just want to browse the internal memory?

http://developer.android.com/sdk/win-usb.html