Macbook won't boot. Stuck on gray apple screen.. :(

[Devcam]

So, here's the deal.
I have a four year old Macbook that's not in the best of shape, but it hasn't failed me like this before.. ever.
I installed a new security update yesterday morning along with the new iTunes, and it worked alright for most of the day.
Around 10:30 or so, it just shut off.
I tried to turn it back on and was faced with the gray apple logo and the horrible spinning icon.
I've tried booting it up in safe mode, verbose mode, and even resetting the PRAM, and nothing works!
The stupid screen stays on for HOURS. No, I'm not kidding... hours.
It eventually did go to a blue screen after maybe three or four hours, (I fell asleep so I'm not sure) but it still wouldn't let me do anything.
Any help?
Please?

 

[spinnerlys]

Mac doesn't boot

 

[halledise]

startup from your install dvd, repair permissions, repair disk.

restart, holding down option+command+p+r for 3 chimes then let her rip.

should be okies now.

if not, restart from install dvd and reinstall the OS

 

[Devcam]

startup from your install dvd, repair permissions, repair disk.

restart, holding down option+command+p+r for 3 chimes then let her rip.

should be okies now.

if not, restart from install dvd and reinstall the OS

Yeap, already done that.
Disk Utilities said my hard drive was ok when I repaired the disk.
A few permissions were fixed when I repaired permissions.
It didn't affect anything at all.
Like I said, I already tried resetting the PRAM.

 

[Hellhammer]

Yeap, already done that.
Disk Utilities said my hard drive was ok when I repaired the disk.
A few permissions were fixed when I repaired permissions.
It didn't affect anything at all.
Like I said, I already tried resetting the PRAM.

Reinstall OS X, it could be a corrupted system file or dead HD (see the link above)

 

[Devcam]

Reinstall OS X, it could be a corrupted system file or dead HD (see the link above)

I can use my leopard installer disc and whatnot, but I would technically be downgrading if I installed it. Would that really be bad?

How would I know for sure that my HD is dead?
I could look at it through disk utilities, and it showed all the correct info about it (like how much space I used, how much was left, etc.).

A big issue I'm having with that is that leopard says it needs 11.4 GB to install on my computer.
My computer only has 10 GB available..

:/