15" Macbook Pro (2007) will no longer boot in any manner. (Please, help.)

Question

Evening, everyone.
I could beat my head against the wall for all the frustration my MBP is giving me! I really hope some kind soul will be able to help me. I will try to be methodical in explaining the whole story of what I have done and what appears to be wrong, so that maybe you fine detectives can pluck out the relevant information and piece a solution together:
I was multi-tasking about two days ago (perhaps too much) and I had installed the most recent OS X (Leopard) Auto-update. I had also downloaded and installed the program "Little Snitch," and both the update and Snitch were asking that I restart. So, I did--sure enough, it went to the spacey-purpley Leopard screen and appeared to have successfully updated. It shut off and began to boot up as usual. However, it appeared to be stuck at the Apple and rotating dial screen, with the bluish-greyish background. All of a sudden, the screen went black and the computer shut itself off completely.
I tried to turn it back on, with the exact same sequence of events. I ran it in Cmd-V mode (is it called.... verbose?) and it mentioned Little Snitch amidst the rest of the report (which is what makes me concerned that it might be the source of the issue). At the end of the repost, it said something about "shutting off the CPU" and "killing all processes." Then, again, it shut itself off completely. I tried Cmd boot up (to select the boot disk, as I have a Bootcamp partition with Windows XP that has never caused me trouble before) and selected the OS X volume. Again, no change.
Finally, I hunted down a friend who had just purchased a new Mac to borrow his OS X install disc. I upgraded to Tiger, so I don't know if that might be why his boot disk did not work for everything I needed it for. I don't have Y disc with me, because I'm from California and I left it somewhere in my office. But, I was able to boot from his disk--although it reported that I "could not install OS X Tiger on this machine"--and use the Disk Utility. I tried to use the verify and repair functions, but they both came back with "sibling errors."
I may have made a crucial error here: I then tinkered with the Open Firmware Password Settings. I tried a few of the things I already had over again, and then went to bed.
Well, that was all last night. I came back from work today, determined to try using target disk mode and my friend's mac in order to solve the problem. I followed all the procedures necessary, plugged in the cable, booted up my kaputnik target computer holding down the "t" key, but my computer was totally unresponsive to the command. Now, NONE of the start up commands will work. I cannot boot from the OS X disc, I cannot run the cmd-v thing, I cannot "Cmd" select a drive at startup... I don't know if this has to do with my setting of a firmware password, because it was not doing any of this stuff yesterday.
I'm freaking out. I'm a student, it's finals time, and I have 3/4 of my thesis on that machine. Please, help me work this one out. Even if it's just a way to get to the hard drive in target disk mode to get those files I need without really fixing the problem. I'll be happy to provide any other information that might be helpful in finding a solution.

Answer 1

Restart with the Option key held down and the Mac OS X install disk inserted, provide the firmware password, click on the DVD, press the button with the straight arrow, access the firmware settings, disable the password, and use FireWire Target Disk mode. If you can't do that or it doesn't work, contact Apple.
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