Sorry I'm just a tad confused here...you say that before your Xbox stopped working, whenever you tried to choose a song in Rock Band it would say Disc Unreadable? That's because either the disc is bad or the drive is bad. Now you're saying the Xbox won't even turn on, correct? Open it up and see if there is any damage to any part inside, then check and make sure every power cable is plugged in. Before you take it apart, lets try the No Power Solution.
First, press the eject button instead of the power button. If it turns on, yay! If not,
Check and see what color the light on your power supply is when you plug it in. If orange, nothing is wrong with the power supply. If it's orange and still doesn't work, go to the next step.
Remove all cords from the power supply, then plug them in again to your Xbox and see if it works. If not, then,
Try another outlet, maybe it's something as simple as that. Again, if it still doesn't work
Let your power supply cool for at least half an hour. Try it again, if it still doesn't work.
Find another power supply, see if that works. If not, take it in to your local console repair shop (or send it to Microsoft, only if you want to wait months for it to return and pay a shit ton [unless it's covered by a warrenty])
Before you send it in, wait for a few more Tempers to check out your problem and see if they know anything as I might be wrong and that'd suck if it was an easy fix and I wasted your time/money.
Hope this helps!
EDIT: Oh and if you could please use better grammar so others can understand you better, we'd be able to solve problems quicker. Not trying to be mean, but every time I reread your first post I feel like I interpreted it wrong the first time...Oh and don't double post either.