I have slightly the same problem with an old MacBook Core Duo:
Yesterday I inserted a DVD, the Mac could not find it so I tried to eject the disc. Because nothing happened, I held down the power button for several seconds to restart the computer while holding down the eject key. Nothing happened at all and since then I just have a white screen when trying to boot.
Holding down the button of the trackpad while starting the computer does not work either.
I'm not sure it's the HD because I don't hear any strange noise from from it.
What I've tried so far:
- waiting for several hours to see if it starts veerrryyyy sloooowwwlyyy
- holding down the eject / mouse-button while starting
- holding down "T" for target mode while starting
- holding down "alt" while starting
- I took out the RAM & the HD and put it back in
Edit: Also tried this...
1. Remove the power supply and the battery
2. Hold the power button for 10 secs
3. Put the battery back in, and the power supply as well
4. Power on while holding : Apple+Function+P+L keys all together …
- press CMD+S while starting
- press CMD+v while starting