HD Dead?

Hello:

13" Macbook running Snow Leopard bought off craigslist about a month ago. It made a loud whirring noise, started acting weirdly and we pushed the power button to turn it off. Upon restarting all we got is the blue/grey screen.

I've tried every startup key combination to no avail.

Using a PC and an old mac I formatted an external HD according to these instructions: Install Snow Leopard from External Firewire or USB Hard Drive, or How to Upgrade to 10.6 Without a DVD Drive - OS X Daily and holding down the option key I DO see the external HD but when I click on the little arrow underneath it nothing happens.

Two questions:
1: When I hold down option on startup I ONLY see the external HD plugged into the laptop and nothing else. Would I normally also see the internal HD? Does this suggest that the laptop's HD is dead, or the connection to the HD is perhaps dead?
2: If I formatted the external HD incorrectly and it's not bootable would it still show up when I start up with the "option" key pressed? Or does it suggest that it is indeed bootable - the fact that it shows up in the "option" list?

Thanks very much.

and holding down the option key I DO see the external HD but when I click on the little arrow underneath it nothing happens

Click to expand...

When u are using Option on boot up the normal scene is that you have 2 or more bootable drives/disks to choose from. As the Ext HD is showing, then 1 click to select which drive and hit return to start the boot - normal drive is not bootable so not showing up.
Seems the OS on the Internal HD is not available so to see where things are at, Boot off the install disk that came with the computer and after selecting language then go for disk utility in drop down menu and Erase the drive. If u cannot do that then good chance the drive is doorstop material.