not too sure. from looking at mine when i go the route you did i get a dropdown box that says pc connection:
options are usb and bluetooth pan.
for tethering, the easiest thing i found to do is to grab the internet sharing fix cab and install this. then use like wmwifirouter or something similar. i know wmwifirouter lets you connect via wifi, bluetooth, and usb to use your phone as a modem.
look here:
http://forum.ppcgeeks.com/showthread.php?t=42730 under internet you'll find stuff your looking for.
also beware that if sprint does catch you doing this, they will charge you for it. hasn't happened to anyone that i know of but it can.