When buying a “packaged” computer, the standard configuration is 1 internal hard drive only. And for more storage, the vendor would offer a bigger capacity of 1 terabyte in lieu of the usual 500 GB. It is the advice of the tech in our office to get 2 units of 500 GB instead of the 1 unit of a bigger hard drive which is cheaper. Having 2 internal hard drives would make the computer faster in its access especially if the files are located in the drive D: instead of all files being in drive C: of the computer.