Deleting duplicate rows on table with/without primary key in Sql Server

Table with primary key

Id    name

1                     Harpreet

2                     Harpreet

3                     Harpreet

4                     John

5                     Smit

select min(id) from #tablewithprimary group name

=1,4,5

Delete from .. where id not in (1,4,5)

Result : 1,4,5

delete from #tablewithprimary where id not in   

  (select min(id) from #tablewithprimary group by course,subject)