USB controllers in Windows, and possibly in other operating systems, are somewhat inclined to corruption of the files that track what device is on which port of the controllers. This is NOT just in drivers, but in the USB control files that are part of the OS systems.

A common cause is disconnecting devices without using the "safely remove" button, although there appear to be other possibilities. With larger drives, if "indexing" is turned on, it may take hours for the background indexing to complete for even a fairly small change in data on the device, and the temptation is to just pull the plug even if the Safe Remove says "The device cannot be disconnected because another program is using it" and you don't have another program visible. The "other program" is usually Windows File Manager, which is invisible to you.

Microsoft has several "comments" on remedies for USB problems, but the bottom line procedure is to remove ALL OF THE USB CONTROLLERS and the rebuild the whole USB setup.

To do this, you need to get into Device Manager and DISABLE/DELETE ALL USB CONNECTIONS, then shut down the computer (SHUT DOWN, not Reboot).

Remove (disconnect) ALL USB DEVICES.

Restart the computer, and turn on ONE powered external device and plug it in, or plug in ONE unpowered device. The Plug-N-Play (PNP) system can then recognize that device and enter it into the controller setup to rebuild the entire setup.

Repeat the connection for each USB device, ONE AT A TIME, allowing each device to be recognized before going to the next one.

A difficulty that Microsoft fails to note is that many people use a USB mouse and keyboard, or "wireless" ones that require a USB dongle plugged into the computer. Earlier Windows operating systems don't identify what device is on each USB port in Device Manager, and once you disconnect both mouse and keyboard it's difficult to complete the process. (Win7 does give "some clues" about what's on each port) You should be able to unplug the device that's "prematurely disconnected," plug it back in and let it be recognized again. If you watch for a "new port" in Device Manager, you may be able to tell which one is needed to finish the disconnecting so you can disable that one last.

Note that this is the "last resort" procedure when all other suggestions fail, but my experience has been that "all the other" suggestions nearly always do fail if you have a significant problem.

Google is, unfortunately, not a very good way to find technical assistance, especially? for Windows, since it lists all of the advertisers who pay for "preference" first, then all of the "most popular" sites next (where all the people who think they know it all go), before you get to the places where you might actually find something useful.

I would suggest that you bookmark Microsoft Advanced Search for use in future Windows problems. This is also "not a very good place" to find information since Microsoft sort of demolished their help system when they figured out that they didn't really know how bad Vista was, but it has begun some rebuilding and is a little better recently. (I usually uncheck the "Microsoft Community Forums" for first searches, and of course you'll want to uncheck others that don't apply to your problem. The "forums" can (rarely) give some clues if all else fails, but you can always go back to them if you don't find a solution.)

I'm not sure whether I saved the instructions above, but might be able to find a link to where I found them. You might want to try some of the other suggestion before diving into this one. IFF I find a link it probably won't happen immediately, if at all.

John