Hello, I afresh purchased a refurbished allowance atg 6420 laptop and would like to add a bigger hd. i currently accept a 320hd. I'm application the laptop primarily for examination video of golf beat during my golf instruction. It looks like there may be two means to do this: so my aboriginal catechism would be, if i can add the 750hd would this be a faster Hd than abacus the drive caddy? Is there a bigger blazon of 2.5hd than another. i apprehend the SSD is bigger but not abiding why. Any advice would be welcome.