No boot and a bomb

My friend has a macintosh computer that will not boot up. She gets a message that reads “extension error, type 41 and contains a picture of a “bomb” (a round object with a fuse). I immediatly think virus, but am not mac knowledgable. Also she does not have the boot or rescue disk that came with the computer. Any help would be much appreciated, also the location that I might be able to download a mac boot disk. One more thing, if I download the disk will I have to do it from a mac machine?