Windows 7: Computer will not boot up

Computer - Sony Viao VGN-CS320J.
Got a blue screen yesterday and then the computer would not boot up. On pressing the start button, the power on light comes on and stays on. Can hear a buzz for a second and then nothing - black screen, no light on for hard drive. Cannot do anything.
Funny thing is that after this happened yesterday, I found out that if I pressed the on button and the dvd eject button simultaneously, the computer booted up. I was able to back up all my files. I then went to the c drive properties to initiate check disk. It told me that it could only be done at next start up. So, I restarted the computer with the above trick and let it check the disk. No problems found. I then rebooted with the same trick and got into bios - reset it to default values. Did not fix the problem. Restarted with the same trick and got into "repair my computer" after pressing F8 repeatedly. Restored the system to previous good boot, etc.
Checked internet for help and noted at one place that the registry might be too long and have many bad entries. Dowloaded a regisry repair probram and cleaned the registry out. After that - no can do nothing!!! On pressing start button, the power light comes on, the dvd drive works, but nothing else happens. So, cannot get into troubleshooting or safe mode by pressing F8 as the computer has a black screen from the very beginning.
Because I was able to get into the computer with the above trick I discovered accidently (pressing on and dvd eject button simultaneously), I believe the problem is not with the hard drive (?). Can anyone help?

mahendra26

It may be the optical drive or it's motherboard controller are causing problems.
I suggest, disconnecting the drive for now, power and data, make sure the drive is not set as any boot device in BIOS setup. Try again !

Thanks for the reply. As mentioned in my post, I am not able to do anything on the computer now. Do you think I shold open it up and diconect the DVD drive cable from the motherboard and try again?