From the Disinfectant 3.7.1 manual:

"You can remove a WDEF infection from a disk by rebuilding the desktop.

See the “Problem Clinic” section for details. It is often easier to get rid

of a WDEF infection by simply rebuilding the Desktop file than it is to use

Disinfectant. This is also the only way to get rid of a WDEF infection under

System 7."