Hello ? I have a question about External and Internal HardDrives. I want to buy Hard Drive because I want my computer Run Fast. Currently I have a hard drive : "wdcwd800jb-00jjc0" I am using "19.25GB" I think it is slow. The question is, Can I replace the hard drive that I already have and use external harddrive as "Main Drive" ? My concern is which hard drive run fast. And tell me what is different (or Ideal) between External and Internal Hard drive. Should I buy Internal or External hard drive ?