Cynthia,
Do you have a boatload of cartridges you want to use with your old machine? Your best choice may be to find a used Explore, Explore Aire1, or Explore Aire2, then "link/register" your cartridges online at Cricut's site. The cartridge port on the early Explores was supposed to be for linking cartridges to your account, but they won't work if you're the second owner. You call Cricut Customer support, they'll give you a code that you write on a piece of paper, then photograph the front and back of your cartridges with that piece of paper and send them the photograph. Reduce your photo to 800px wide, though, because their email system discards really big files. Once your cartridge is "registered" you can use it with Design Space and your Explore a lot easier than the old Design Studio software.
Hope this helps,
Paul Race Hobbycutters.com