WM/Sad is a simple Word macro virus that does not do anything but replicate.
It infects the global template when an infected document is opened. After that every closed document will be infected.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
It contains the following macro description:
Installed to your NORMAL template as AutoClose to clean the prank macros from any documents that you open then close.
This description is on "AutoClose" macro in the global template, and on "Sad" macro on infected documents. It is viewable from "Tools/Macro" dialog.
Technical Details: Sami Rautiainen, F-Secure