Moving Preferences.txt location not working

Hi All, I am trying to move the default save location for the preferences.txt file using the entry "settings.path=U:\arduino" but it seems to be ignoring this parameter. The folder does exist and I have changed the sketchbook path successfully already. I have tried forward slash as well "/" but that didn't work either. We are running UNO's with v1.6.5-r5 on Windows7. We would like to set the default location as students do not have access to the APPDATA folder and they do not use roaming profiles, this would allow the settings to follow them as they move from PC to PC. I hope someone can help. Thanks