Windows treats the iPhone as either a digital camera or a file system, depending on how the photos are accessed. On a Windows PC, the easiest way to get pictures from your iPhone is to just use Windows Explorer, but there are two ways to go about this. In either case, unlock the iPhone before beginning, or else the photos may not be visible.

Using Windows Plug & Play
This utilizes the pop-up that shows by default in Windows when a device is connected to the computer by way of USB.

1. Plug-in your iPhone to the computer without iTunes running
2. Wait for a popup asking you what you want to do with the device
3. Select “View Content”
4. Find your photos through the folders that are displayed
5. Copy the images from Windows as usual

Using iPhone as Digital Camera in Windows Explorer
If your iPhone is already plugged into the PC, you can also try this method:

1. Open “My Computer”
2. Find the iPhone, it will appear under Portable Devices section
3. Open iPhone to find your Photos
4. Select the pictures you want to copy and paste them to the desired location of your computer

Remember, if the iPhone pictures are not showing up in Windows, make sure the iPhone is unlocked first. Otherwise the iPhone will be found in ‘My Computer’ but all of the content on it will be invisible and inaccessible. If you run into that, all you need to do is touch the iPhone, unlock the screen and enter the passcode, and all of your stuff will be visible as expected.

see: http://www.m2mate.com/resources/5-ways-to-transfer-iphone-photos-to-computer.html