I had a very similar issue.
I put in a blue-ray disk and went to pause it, but hit stop by accident. My Xbox froze and so I turned it off and back on. This led to whats known as the black screen of death.
Fixes include a hard restart where you hold the power button until it turns off and then you turn it back on. I unplugged it until the power light on my power brick went out. I even power cycled the xbox by both the power button and the outlet. Nothing worked.
A lot of times when an electronic system freezes it is a sign of overheating, which if you read other forums that tends to be the case. Even earlier answers involve reducing the stress on the system by unplugging drives.
So to fix the issue indefinitely
1. Open the xbox case via diagrams and instructions
2. Once open remove the cooler from the CPU.
-You will notice that the heat sink paste will look like dried play-doh.
3. Clean old heat sink paste off with rubbing alcohol (90% preferred), both the cooler and CPU.
4. Apply new thermal paste to the CPU.
-Either a drop the size of a pea or use the spreader that comes with the paste to cover the entire cpu.
5. While the Xbox is apart blowout dust from the entire case with compressed air meant for computers.
6. Put it back together and turn on.
This will resolve most Black screens of death.