This .PIF file worm spreads using mIRC.
It modifies C:\mirc\script.ini and will attempt to send itself to other IRC users from the infected users machine.
This file should be deleted.

A significance of this worm is that even if "show extensions" is selected
the extension does not show for this file.
As anattachment it might be seen as "movie.avi" without the .pif
Also in a browse of the folder where the file may be located, the .pif extension is not visible.