Download MiPhone Tools v.20140509 from here, here or here. (26 MB) You can download a newer version v.20141107 from here.
The package contains MiPhone Tools:
• Google ADB tool and driver
• Microsoft MTP and RNDIS driver
• Qualcomm USB serial driver
• Xiaomi MiFlash program
After installation, please follow these steps to access internal storage
• Launch ‘Settings’ application
• Switch to ‘COMPLETE SETTINGS’ page
• Enter ‘Storage’ item
• Select ‘USB computer connection’ from menu
• Check ‘Media device(MTP)’ option
After driver finish installation, open file explorer to access internal storage.