Try no hard drive. Just the DVDRW. Place your working Ubuntu LiveCD (see google) in there and try to boot the LiveCD. I must decline from duplicating what the Ubuntu LiveCD is and how we use that but it's a test I use to see what to try next.
Remember to unplug ALL USB devices as some can cause this issue.
The laptop is an HP Pavilion dv5t-1000.
It has 4GB of RAM, an Intel Core 2 Duo processor, and I think 320 GB hard drive.
The product number is kq574av.
I can set the BIOS settings, I can select the drive to boot from (CD or HDD), but when it tries to boot, it just shows a black screen perpetually.
I've tried swapping HDD & DVD drives as well as RAM from a good computer, all to no avail.
Any other suggestions for testing and figuring out what is going on with the computer?