You have to log the data in some way manually. My favorite is to include CREATE and UPDATE columns on each table as such:
ALTER TABLE TableName ADD [CREATE_TIMESTAMP] datetime NULL DEFAULT (getdate())
ALTER TABLE TableName ADD [CREATE_USERID] varchar(30) NULL DEFAULT (suser_sname())
ALTER TABLE TableName ADD [UPDATE_TIMESTAMP] datetime NULL DEFAULT (getdate())
ALTER TABLE TableName ADD [UPDATE_USERID] varchar(30) NULL DEFAULT (suser_sname())
Then add a trigger to force the update of the UPDATE columns.
After that you can tell who inserted or updated a row. Still can't tell a delete though. You would need a log table for that. Basically create a table
TableName_Log that has the same structure as
TableName then a DELETE trigger that moves the deleted rows (updated too if you want) into the log table.