hm, i tried that and it was the same as before. the mouse shows up and i can move it for about 5 seconds before the computer goes back into its coma.

I will predict that you will not be able to do more testing until you replace the hard drive.

Nothing else has worked, so try this:
battery in, power adapter plugged in.
Press and _hold_ the power switch. You should hear an extra long tone, and then you should see the light in the case latch start flashing. I'm not sure of the sequence of those two things happening, but when the second happens, you can release the power switch. If you get nothing else after that (wait for a couple of minutes just to make sure), press and hold the power switch until your MBPro shuts off. Remove the battery, unplug the power, and then press and hold the power switch for 5 seconds, and release
battery, and power adapter back in. Power back on normally, and try to boot to your restore DVD (just on a chance). Hold the C, and no other key along with the C. Make sure that nothing else is attached to the MacBookPro, except the power adapter.
If you don't make any other progress this time, then I think you are done, get some service.