Q:  How do I uninstall the PL-2303 MAC X driver? 
  
A:  1. Open "Applications-> Utilities-> Terminal". You need to create ID & password first on NetInfo Manager.

2. Login to root user and type "su" and enter password.

3. Type "cd /System/Library/Extensions" to go to the "Extensions" folder.

4. Unload the driver (if it had been loaded) by typing "kextunload PL2303.kext" or "kextunload 
ProlificUsbSerial.kext".

5. Remove the driver by typing "rm -r PL2303.kext" or "rm -r ProlificUsbSerial.kext".