I'm assuming you're using a Windows PC. If not, someone with a Mac will need to help you.
- With your iPhone connected, Open My Computer
- Right Click on your iPhone, Select Properties
- Click the Events tab
- Make sure Select an Event is set to Camera connected
- Select the Take no action radio button
- Click Ok
- Open Control Panel, Hardware and Sound, AutoPlay
- Scroll down until you find your iPhone in the list
- Change the drop down field for your iPhone to Take no action
- Click Save
Hope that helps.