Macbook shuts down within 20 secs, but booting from CDs fine

Hi all,

I'll jump straight in: I have a black MacBook 13.3", 2ghz intel core duo, model MA472LL/A

Within 20 seconds of powering on and OSX is loading, showing the grey Apple logo screen, the Macbook will turn itself completely off without warning. I've tried booting from the Leopard DVD, which is completely stable and attempted an archive and install and even a fresh erase and install but the machine will freeze when installing files.

TechTool Pro has checked out all the hardware, and done a full surface scan of the HD which has come back clean.

Target disk mode works fine and I can see the drive from my trusty iBook. Eventhough I started an erase and install previously it's obviously not got as far as erasing the drive since I can see my files still.

So... what can I do? Is there a log file I can check to see what's caused the shutdown, assuming the error was captured in time?

Any help appreciated!

Boot from the Leopard DVD, go into Utilities, select Disk Utility and run Repair Disk and see what is reported there. Also check out the drive has been partitioned, even if only the single partition, GUID partition table selected, and the drive has then been formatted.