If Apple was so kind to give you tethering (and didn’t silently remove it after an update), or if you just happen to have enabled it using, let’s say, the alternative method. And you happen to be forced to use Windows, and you really are tired of XP, and Vista surely isn’t an option; you’re probably running Windows 7.
To enable tethering on the iPhone + Windows; just pair the bluetooth devices (I actually haven’t tried with USB yet, and don’t really plan on doing that), Windows will start to QQ about it being unable to find a suitable driver for the iPhone… I even installed iTunes to see if the message would go away, but apparently it won’t. I’ll have to do some more Googling later on.
Anyway, to tether, just go to “Control Panel” > “View devices and printers” (under “Hardware and Sound”) > Devices > $iPhone_Name (it has a fancy yellow warning sign next to it…).
Right click, “Connect using” > “Access point”.
Simple enough. Pick “Public network”, just to be sure (though, your ISP should already block most direct connections between devices, and your iPhone won’t forward any ports I guess/hope).
And don’t forget to disable WiFi or unplug your network cable if you want to test it at home.
Oh, right, and I probably should give you a bunch of warnings about data consumption and that AT&T might brutally murder you and your family if you dare using tethering (as far as they can actually check you’re tethering, and if they can, I’m pretty sure they’ll be violating a couple of privacy laws). As for the customers of the 95% other decent providers who allow tethering and aren’t living in the middle ages, have fun using it. Finally work can be done on the train/while waiting/… 😉