Query the Owner of SQL Server 2008 R2 Jobs
This will generate the commands to change all non-sa-owned jobs to sa. You just need to copy and paste from the results pane to the top pane (or a new query window), and execute.

SELECT 'EXEC msdb.dbo.sp_update_job @job_id = ''' 
        + CONVERT(VARCHAR(36), job_id) 
        + ''', @owner_login_name = ''sa'';'
    FROM msdb.dbo.sysjobs
    WHERE owner_sid &lt;&gt; 0x01;