hard drive problems - not showing up anywhere

so im sure you all see this problem all the time. it happened to me last night as i was finishing up a song on garageband. im pretty desperate to get help for this, to the point where i signed up here for the sole purpose of posting this thread, so i can get personal help. ive found problems close to mine, but not exact. so heres the story:

oh i have a 13" macbook, running leopard 10.5.4

last night i was just finishing a song on garageband. i changed the output from a gearbox i have to the internal speakers. the box popped up, "are you sure you want to change this, this may take a while blah blah blah" so i clicked yes, it was loading, and as it was loading, i got the "you need to restart your computer". so i held the power button until it shut down, and when i turned it back on, it went to the greyish bluish screen, stayed blank for a minute, then i got the dreadful folder with a question mark. i thought nothing of it, but at the same time i was very scared, both for the reason that ive never heard of this before. so i restarted my macbook, and it happened again. all i got was the folder with a question mark.

i spent all night last night hunting around until about 4am when i gave up. this happened around 7pm. i found forums saying "insert the recovery cd" but whats the recovery cd? all i have are install disk one and two, are those the recovery cds? i ran a diagnostic test, both regular and extended, both found no problems. i didnt even have to hold c when i put install disk one in, it automatically booted from the cd. i followed the instructions until i got to "Select a Destination - where do you want to install?" and the whole box was blank. nothing greyed out, nothing there at all. just completely blank. i went to disk utility, all it picked up was my cd drive and the install cd. nothing greyed out there either. i saw a forum where the person was having a similar problem to mine, and said they went to system profiler and their hard drive was under "serial ata" so i tried that. all that was there was "Intel ICH8-M AHCI". if this helps, heres what it says underneath:

"Intel ICH8-M AHCI:

Vendor: Intel
Product: ICH8-M AHCI
Speed: 1.5 Gigabit
Description: ACHI Version 1.10 Supported"

now i dont know if thats my hard drive, im new to macs and their hardware. but if it is, i find this very weird, because at some times ill hear the hard drive humming and revving up, and at other times its completely quiet, and its not being picked up anywhere else.

ive tried everything i possibly can, i cant run it in safe mode, i made sure the hard drive was in all the way, jiggled it a bit...i dont know what else to do.

im very desperate, ive never heard of this happening, so i never backed anything up, but the only really important things i had on there were a few songs i wrote, which i sent to friends, so its not like they cant just send it to me. but ive learned my lesson from this, im gonna back up all my **** every day once i get this fixed.

so please give me any help, even if it involves completely wiping out my hard drive, since i already accepted that i pretty much lost everything on there. if you can help me fix this without losing everything (which i most likely already have), thennn...to me, you are jesus resurrected.

thanks in advance, sorry about the wall of text.