How do I put an SSD inside of a Dell Inspiron 660?

First off, I just want to express how much I love your computers, Dell. You guys ROCK! Best computer brand I've ever bought. Onto the topic; I have a Dell Inspiron 660 desktop PC with a 1 TB hard drive. I want to upgrade the hard drive to an SSD, but I looked inside of the PC case and the hard drive has 2 metal rails (one on each side). That being said; How would I stick an SSD in there? I know I need an adapter of sorts that will let it fit in there, but how would I do this considering the way the hard drive is set up? I'm so confused! Thanks for your time.