A family of Microsoft relational database management systems designed for ease of use.
PS: You do realise that what you are attempting will delete all rows which are duplicated on the two columns in question? Is this what is intended? For examples of how to delete all bar one of duplicate rows see DeleteDemo.zip in my Dropbox public databases folder at:
This little demo file illustrates two queries which will delete all duplicates bar one, in one case using the primary key to determine which row to retain, in the other using the value of a non-key column.