If you HTC Incredible wont turn on you might need to do a hard factory reset. This will restore the phone to the factory settings (The same state as when you got it) but it will erase all data on your phone meaning only do this, if you're sure you've exausted all other options. The steps for a factory:
1) Turn off your phone and remove the incredible's battery. Wait a few seconds and then reinsert the battery.
2) Press and hold the Volume down buttion and then quickly press the power button until the device turns on.
3) Wait for a screen with three Android images/Menu to pop up and then release the volume down button
4) Select a factory reset/Clear Storage and then press the power button again. Make sure your phone is full charged before to do a factory reset!
Hope you get that sorted out. And remember the factory reset should be your last option so make sure you've tried everything else you can think of before hand.