Cannot install Snow Leopard on MacBook

Hi,

I'm trying to install OS X Snow Leopard (10.6.3) on a MacBook A1181, on which Tiger (10.4) was probably installed but corrupt.

After the CD was inserted, I can only see, during minutes, the light grey screen with the rotating wheel.

I can hear a strong air flow, like the fan is running fast.

Pressing C during startup does not change anything,
(nor does resetting the PRAM, or booting in single user mode).

When pressing "Alt" during startup, I see a "Lock" icon with a field asking for password and the disks are not listed.
Does this mean that I need some administrative password to make the install ?

Thank you for your help.

That sounds like the Firmware password to me.

Which exact Mac is this?

The MacBook is a black A1181.
Under the battery is also written EMC 2242.

How do I install Snow Leopard ?
Do I need to press the Alt key, enter the password and select the CD drive ?

When just putting the CD into the bay, I just can hear the CD rotating and see the rotating wheel.

Do I need the firmware password for this ?
I'm unfamiliar with Apple products, but this sounds strange to me.

The only reason you'd need a firmware password is if someone had set one. This isn't, brand new, out-of-the-box behaviour. Someone has deliberately set a firmware password.

You'd normally set it to prevent someone knowingly or unknowingly altering the system. So yes, upgrading the OS would fall into this.

But yes, holding alt/option on the keyboard as the Mac boots will give you a list of bootable devices. The Snow Leopard disc will be in this list. You select it and away you go. All providing you have the password.

And you do need that password. Anti-theft measure also File Vault.