1) OneNote OEM comes with Surface Pro 4. OneNote is a stand alone version 17.6366.15651.0. a) Is linked with the pen. Top eraser button opens OneNote OEM. b) Cannot be customized, uninstalled or changed, but can only be pinned to the taskbar or start menu. c) Cannot be used with the handwriting recognition functionality in Windows (i.e. Ink to Text or Ink to Math). 2) OneNote 2016 comes with Office 365. One Note does not have a version number but is part of Office 365 version 16.0.6001.1041 a) Cannot be linked with the pen. Top eraser button cannot open this. b) Customizable full version that can be uninstalled or changed. c) Full functionality of handwriting recognition in Windows (i.e. Ink to Text or Ink to Math). The file associations and protocols could not be changed from OneNote OEM to OneNote 2016. This week, Windows 10 v1511 build 10586 changes that. Some, but not all of the default file associations and protocols from OneNote OEM to OneNote 2016 were changed automatically with this Windows update. After this Windows Update, the pen had to be rebooted by removing the AAAA battery and re-pairing the Bluetooth device. It looks like because of the cmd protocol association, the pen top eraser button STILL CANNOT open the full version of OneNote 2016. OneNote 2016 extensions : .one, .onepkg, .onetoc, .onetoc2 OneNote 2016 protocols : ONENOTE URL:OneNote Protocol, ONENOTEDESKTOP URL:OneNote ProtocolOneNote OEM protocols : ONENOTE-CMD URLnenote-cmd PLEASE UPTICK THE WINDOWS FEEDBACK COMMENTS ON THIS ISSUE IF YOU USE HANDWRITING RECOGNITION WITH THE PEN. Many of you may be in the business of quickly jotting down important information that is barely readable. Less of you have probably gone through the utterly buried 50 sentence training that Windows - Control Panel - Clock, Language, and Region - Language - Language Options - Handwriting Personalization - Teach Recognizer Handwriting Style performs to correctly identify "hen scratch". The potential correction in this lapse in functionality will enable a real productive use of the top eraser button of the pen! Thank you!