Exactly what happens when you try to start up?
Five ways to eject a stuck CD or DVD from the optical drive
Ejecting the stuck disc can usually be done in one of the following ways:
1. Restart the computer and after the chime press and hold down the left mouse button until the disc ejects.
2. Press the Eject button on your keyboard.
3. Click on the Eject button in the menubar.
4. Press COMMAND-E.
5. If none of the above work try this: Open the Terminal application in your Utilities folder. At the prompt enter or paste the following:
If this fails then try this:
Boot the computer into Single-user Mode. At the prompt enter the same command as used above. To restart the computer enter "reboot" at the prompt without quotes.
Pressing down the track pad while starting did not help.
The battery is charging, and 4 diodes are on, and the fifth is blinking. To me it seems like there is something wrong with the program or circuits which should run the starting procedure. The error is not connected to the HD as I have changed the HD. Both HD used is working fine and can be used to run another MacBook Pro using an USB connection.