Yup, I made sure to double-check the jumpers!
* * *
Follow-Up... Well, I double-checked everything and pushed on everything to make sure it was seated okay, such as the video card and the RAM, and did the same with all the cables in the back. Then I crossed my fingers, toes, and eyes, and tried turning it on again. And it booted up just fine!
So now I am formatting the new drive.
Thank you all! I love this place!