How to disable Microsoft Office keyboard shortcut (Shift-Crtrl-Win-Alt)
Disable:
REG ADD HKCU\Software\Classes\ms-officeapp\Shell\Open\Command /t REG_SZ /d rundll32
Enable:
REG DELETE HKCU\Software\Classes\ms-officeapp\Shell\Open\Command
Many thanks to this post on superuser.com.