Flashing folder with question mark, please help!

my comp froze up and then when i try and restart it it flashes a folder with a question mark. i have a macbook. i did the hold the power button down for 10 sec thing and restart with the option held down. the cursor comes up but the hard drive dosent show up ever. then i tried to reinstall the mac osx disk and i get it to the point where it asks me to choose my hard drive and theres just nothing to choose from.

i did the hardware test and it came up with nothing wrong so im pretty sure that its a software issue.

i also reset the ram thing and that didnt work.

i think i have a virus because my friend was on my comp downloading something i think. anyone have any other possible solutions?

thank you very much!

Mine was like that before... So, what's the result? Well, my hard drive was dead. Bring your Mac to apply store so they can check the condition of your Mac. Good luck.

wouldnt a dead hard drive show up in a hardware test?

No it will not be a virus.

Get your install DVD, assume you have it, and boot holding down 'C'. Go to Utilities and run Repair Disk and let us know how you get on?

ok so i ran repair disk. it came up in red saying "invalid b-tree node size" "volume check failure".

anyone know what this means?

thank you very much!

First question you ran Repair Disk whilst booted from the install DVD and not the system operating system?

If so time for DiskWarrior!

ya i ran disk utility through the install disk. how much would this cost to fix at the apple store?

will disk warrior fix this or is there a chance it wont?

thank you for your help!

i was reading up on other possible solutions and came across the single user mode solution. except when i hold down the apple + S keys nothing happens. i read that you press power and then immediatly hold the apple + S keys to enter single user mode. is this correct? is it possible that my computer just wont allow me to enter single user mode because of my hard drive issue?