Can't connect phone to computer, but its taking a charge.

I am about to get a new phone and need to transfer pictures to my computer. However, my iphone refuses to connect to my PC (Windows 7). When I plug my phone into my computer through the USB it begins to charge, but it doesnt show up anywhere. I tried going through accessories>printers & Hardware but nothing. Tried to go through my computer but again couldn't find the device. Just looking for a way to back up my pics and videos without having to screen cap all of the pics to transfer them to my photo stream. I know when i plug it in the camera wizard should automatically pop up, but no luck.