It is very handy, after attaching the iPhone 4 to the Toshiba by USB cable, when the iPhone 4 shows up as an external drive in the "computer" list in Windows Explorer on my Toshiba Satellite running Vista Home Premium. That enables easy exchange of the pictures taken on the iPhone to the Computer, without having to email the pictures.
Sometimes Vista recognises the iPhone as an external drive, and sometimes it does not.
In either case, Device Manager under Imaging Devices, shows "USB 2.0 HD Camera" instead of iPhone.
I have tried different USB cords, different USB slots, repairing iTunes 10.5, and uninstalling iPhone drivers and reinstalling.
Also intermittently, sometimes iTunes reports "iPhone attached but cannot read information, unplug and reattach", or words to that effect. The strange thing is that the situations do not correlate. When Windows Explorer does not list the iPhone, iTunes may pick it up with no problem. I believe it also happens that sometimes iTunes cannot read the iPhone but Windows Explorer lists it (difficult to check the facts since cannot reproduce problem at will).
Once or twice Vista also reports "installing driver" when iPhone attaches, but it always finds the driver.
Any thoughts short of reinstalling Vista. Away from home for the next 2 weeks so have no disk to try a Vista repair.