Ran update to 10.4.11 and now it wont boot

Question

Last night, I tried to update to ver. 10.4.11, and now it will not boot.
The reason I ran the update is because I downloaded an application called Sandvox, got a message that it could not install on my current OS and I needed to update to Leopard or Tiger. I was already running 10.4.10, and I thought that was a weird message, so I thought maybe there was an update that I needed. I dragged the Sandvox application icon to the trash can- and checked to see if an update was available and saw that there were 3 updates available. The first update was for ITunes, second one I don't remember, third one was 10.4.11 intel chip something. The first 2 updates were successful, the third update for 10.4.11 failed to install and I got an exclamation mark next to it and it stated it was unable to install and that the application had been moved to the trash and in order to successfully install the update it would need to be taken out of the trash. Then I got a second pop saying my computer needs to be restarted (i'm guessing because of the other 2 updates that ran successfully). I had to force quit safari to restart- and had to force it to shut down by pressing shift and power, then ctrl and power because it would not respond to anything else. I'm not sure which one of those combinations of keystrokes got to to shut off- but one of them did. Then it just would not boot after that.
When I try to to boot it I let it sit for 10 min, but all I get is a grey screen with an apple and a spinning circle thing, and the computer gets MUCH hotter than usual and the fan kicks on and spins very loudly- much more loudly than usual. So I just shut it off in fear of doing damage by heat.
This is my only computer, so I've had to come over to a neighbors house and ask to use their computer to try and find some help-
I would really....really appreciate any help. I have so many thing I have to get done, and this is my only computer. Thank you very much in advance for anyone who can help.

Answer 1

Thanks Hans for the suggestion, but I do not own a copy of DiskWarrior. I think that because I don't own any disk utilities other than what are on the OS X install disk, I will try those tools for now. The archive and install function sounds a little nerve wrecking- I'm guessing it means it will archive any user files, and overwrite any system files? Because I can't boot the computer I am not able to backup some of my recent work before doing this. Should I expect the wost when doing this- or have people used this function without the loss of any files?
UPDATE: The person who is letting me use their computer found a DW utility and they are currently waiting for the files so I can copy them to a CD. It is labeled as DW 4 and the .rar says it will create a bootable cd. Should I hold of on any action until the DW disc is ready? I guess there is a chance the file will not be complete, or be a fake- I will be extracting it and burning the disc on a PC.....
Message was edited by: Elektrobot