button at the bottom of the screen in MediaTransfer and then click the 
button.
To allow MediaTransfer on your iPhone or iPad to talk to your Windows machine, you need to turn on FTP services (Which are not installed by default in Windows) and then allow incoming connections through your firewall for the FTP itself and also the protocol that allows your iPhone to find your PC in the first place...
Click here to watch a video of how to set up your PC with Windows Vista or 7
Detailed, step-by-step setup: