The easiest way would be to use SQL SERVERS PARSENAME function,
Example:
SELECT
PARSENAME(REPLACE(fullname, ', ','.'),2) AS Surname,
PARSENAME(REPLACE(fullname, ', ','.'),1) AS Forename
FROM names
This would return:
Surname Forename
--------------- --------------
Smith John
(where fullname = "Smith, John")
This of course assumes 2 names only, surname, forename