This article is from the Macintosh system software FAQ, by Elliotte Harold email@example.com with numerous contributions by others.
You need to put the file "DA Handler" in your System Folder. It
should be on one of your System 6.0.x disks. Under Finder the Desk
Accessories load into the memory provided by your application.
Under MultiFinder they load into their own memory space provided
by DA Handler.