Updating 350 Million Records from other table taking too long

Hi,

I have a table1 with new column that needs to be populated from table 2. Table1 has 350 million records in it.

Below is the code i am using... But it takes too long even to update the 1 million

  DECLARE @BacthRecs int 
		SET @BacthRecs = 1000000
		WHILE @BacthRecs = 1000000 
		BEGIN
				UPDATE top ( 1000000 ) a
				SET a.NewColumn = isnull(t.Column1, 0.0000)
				FROM Table1 a with (NOLOCK) INNER JOIN Table2 t with (NOLOCK)
											on   a.Year = t.Year
											and a.ZipCodeKey = t.ZipCodeKey
				WHERE a.year = '2013' 
		SELECT  @BacthRecs = @@ROWCOUNT
		END

Is there is any other way to make it fast? Please let me know. Any help is appreciated.

Thanks,

Punia