Thanks for the quick response w_bovine.... but.....
I'm not talking about using the USB cable.....strictly just mounting and un-mounting the SD card from the settings screen on my Vibrant while not being connected to my PC.
Let me explain. I keep highly confidential Documents, Video files, & Audio files on my external SD card, whereas my other non-confidential files are saved on the internal SD card, both being 16Gb cards. While both cards are mounted, if I go into the app that accesses the confidential files, it keeps a history of files accessed so its easier to find/open them, however, when I un-mount the external SD card, the history of the confidential files disappears because the app can't see the files anymore.
So..... what I want to do, to keep my confidential files away from prying eyes, is a way to be able to mount the external SD card when I need to access/edit the files on the external SD card, then, once done, un-mount it again, so they're not readily available to, lets say for example, family members who like to play games with my phone. I work for an organization that takes its privacy very seriously, so I thought that if I can un-mount the SD card, and no-one knows its there, its the "out of sight, out of mind" theory. If no-one knows the SD card and its files are there, they have no reason to try to access the files, because they're not seen by any of the apps. But I don't want to have to reboot my phone every time I want to access the files, do what I have to, then un-mount the card again to hide the files.
I know there are apps that allow you to encrypt files, but I can't risk the encryption failing and corrupting the files, so if possible, my preference would be the ability to mount and un-mount the external SD card at will.
I hope this clears things up a bit and makes sense....