Why will my Mac not read the hard drive or boot up?

My early 2008, pre-Unibody MacBook Pro (A1226) froze one day and upon restart, the screen stayed a bluish-white, showing only a file icon with a question mark in it.

Based on solutions from the Internet, I first used the Mac OSX install disk to see if the computer was reading the hard drive (checking the Disk Utility); the hard drive was not being read.

So, based on more Internet solutions, I then checked the connection of the hard drive cable. After verifying that the computer was properly connected, I re-checked the Disk Utility and the hard drive was still not being read.

Finally, again based on online solutions suggesting that the hard drive cable may have gone bad, I ordered a replacement hard drive cable from iFixit, installed it, and then re-checked the Disk Utility. The hard drive is still not being read.

Does anyone have any idea what the other causes could be?

I should also note that about six months ago the logicboard stopped working; I paid the flat "depot" rate for Apple and sent it away to be fixed. They said that they checked everything and it all was in order.

Any guidance that any one could provide would be much appreciated!