How to Connect An iPhone 4 to a Computer
The iPhone 4 allows you to play and purchase music. Users can connect to iTunes through their device or by connecting the phone to a computer. If you are just looking to purchase new music to play on your phone, browsing songs through your phone is the most efficient way to do this. If you want to transfer mp3 files to your computer, you will have to connect your iPhone to your computer using a USB connection. Errors occur often when you attempt to sync your phone to your computer. If these errors do occur, you can take a few easy steps to get the device to show up in iTunes.
Disconnect all USB devices from your computer except for the one connecting the phone. Try multiple USB ports on your computer if it still fails to recognize the device.
Turn off your phone by pressing and holding the "Sleep" button on the top of the phone and then dragging the slider on the face of the device.
Turn your phone back on by pressing and holding the "Sleep" button once again. Sometimes your phone just needs to be turned off and back on again for the computer to properly recognize the phone through iTunes.
Make sure your iPhone is charged and still on once it is connected to the computer. Your phone will turn off without warning even if it's plugged into the computer. Make sure it has enough battery to last the entire time you are connected through the USB.
Download and then install a new version of iTunes. iTunes is always available through Apple's website.
Disconnect the USB connect and restart your computer. Once the computer has rebooted, plug the phone back into the computer.