Product Family: Act!
Product: Act! Pro, Act! Premium, Act! Premium (access via web), Act! Premium Cloud
Version: 2005 and later
By putting quotation marks around the template name when saving the document it will save as an .adt document. For detailed, instructions please see the following knowledgebase article and follow Option 2: Put Quotations around the file name:
Templates are saved as Microsoft Word Documents (.doc) instead of Act! Document Templates (.adt)