The problems started first with a several crashes. Followed by crashing at start up. It would show the grey screen with the apple + spinning wheel then would crash and start itself all over again.

We took it to apple store and they replaced the logic board. They then replaced the HD(with a new system software) after they sent it back and it couldn't find the drive to boot off.

It was running fine for a day. Then we did a restart and it again can not find the HD to boot off. I held option on restart and it found the drive...then crashed again once it loaded.

The apple store has been very difficult to deal with. I was hoping there is a solution out there.

Could be a bad power supply if its shutting off completely. Try re-setting the SMC by disconnecting the power cord and holding the power button for a good 10 seconds.

If you have another machine or can use one, try a portable drive with a system on it, see if it will boot from that, (you might have to hold the alt key while you boot) That will let you know if it's the hard drive (I suspect the HD or controller board) or another problem.