I recently bought the DELL INSPIRON 15-7559. It comes with 4 GB DDR3L RAM. I have an old HP laptop which I don't use anymore. It has 4 GB DDR3 RAM. If I add the RAM from the old HP to the Dell, how will it affect its performance? Will it be better with the extra 4 GB of RAM, or will there be compatibility issues? This might be a really basic question, but I'm a noob so bear with me folks! Thanks!