If the workbook  has never been saved as an xls file then closing it
without saving it means it won't exist and so it will not have to be
deleted!
The following vba code should quit excel completely:

Application.DisplayAlerts = False
Application.Quit

This next bit should close a workbook without saving:

Workbooks("BOOK1.XLS").Close SaveChanges:=False

or if you don't know the name of the workbook:

Thisworkbook.Close SaveChanges:=False