LaQuita, my machines both use a flash drive, but I cannot imagine keeping all my designs on one! After collecting designs for two or three years I have thousands and they wouldn't fit. I have them all on my computer (backed up on disk, on a second computer and to an online backup service).
This helps in several ways:
1. I have a program that visually displays PES and other files so I can see what they are
2. I can open the color charts and convert their colors to the threads I have on hand
3. I have all my designs organized in folders by category and by what makes sense to ME.
Hard drives will fail eventually, so be sure you have several methods of back up and do it once a week.