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.
Allow F-Secure Anti-Virus to disinfect the relevant files.
For more general information on disinfection, please see Removal Instructions.
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