It is a hardware problem--check that it is plugged in!
Yes, if the iPhone has a USB port it can be configured to access files on a USB hard drive plugged into that port. However as I don't have an iPhone I cannot give you details on what settings might be needed on the iPhone.
Plugged fuel filter? Plugged air filter? Plugged catalytic converter?
Do you have backup software installed that is mapped to an external hard drive? The software might be automatically trying to backup your files, but the external hard drive is not plugged in.
a flash drive
what is the difference between drive and machine
No a user defined in active directory cannot access a shared drive if they are not part of the domain. You will need to set them up as a user on your computer.
there is no drive cycle for a catalytic converter it could be plugged up....
Depends. Did you have My Computer pulled up the moment you plugged in the USB? If so, close the program, wait a couple of minutes, then try to access the device again. If it still does not show, then you have a faulty USB device and you will need to buy a new one.
There are a couple of ways. Many phones offer access to internal or external disk space by mass storage mode, similar to any USB flash drive. There are _rare_ viruses that propagate by attaching themselves to storage devices plugged into your machine. The thing is, this is is not a big threat at all. Mass storage devices cannot autorun in Windows. Most it could do is add an extra option to the device action list that the user would then have to choose.
no a hard drive has a much faster access time...
It allows the user to assign a standard local drive volume letter (like C:\ or D:\) to a drive on a remote machine connected to his computer over a network. Drive mapping allows a Windows user to access the mapped drive quickly. It can remain in a user's drive tree indefinitely, allowing that user to access a remote drive whenever he wants, without having to reconnect it each time he turns on his computer.