I was preparing for rooting my phone and reading guides on the forum when I came accross this guide on how to mount and turn off USB storage: MicroSD Mounting | Root Your Droid.
But I don't have the pop-up window when I connect to my PC. All I do is click the USB notification and select from Phone Portal, Multi Media Link, another option (which I can't recall clearly at the moment) and None
I also cannot find the "Turn off USB storage" notification after the USB wire is connected. All I can do is unplug my stone directly from my PC.
Do you have the pop-up and notification on your phone?
By the way, I bought my stone from UK.