When you plug an iPhone into a Windows VISTA/7 computer, it should recognize it as a camera device even if you don’t have iTunes installed. This can be useful if you just want to transfer some of your pictures quickly off of the iPhone without installing iTunes and syncing and all that. If your screen locks on the iPhone, however and if it was locked while you plugged it into your computer, then the DCIM folder that typically contains all the pictures on your camera roll will be empty (security). Here’s how to your pictures:
[step 1] Unplug your iPhone from the USB port.
[step 2] Unlock your iPhone screen.
[step 3] Plug your iPhone back into the USB port and open the Camera DCIM folder using explorer. NOTE: your images are now visible.