Error installing snow leopard. Shows Folder with question mark

Im using a macbook 10.5.8 leopard. recently I just installed snow leopard using the installation disc and through the installation process the disc stop running and prompted "an error occurred while installing mac os x snow leopard." I then tried to erase my macintosh HD and reinstall the disc again. This time round it prompt "install failed. Mac OS X could not be installed on your computer. The installer encountered an unknown error that failed the install. please contact the software manufacturer. " after ejecting the disc and restarting, it shows a folder with a question mark blinking. I tried to follow some of the methods like holding the alt key when inserting disc to reinstall but it doesn't go to installation page, restart PRAM, erase the HD Again etc. Now it say "mac osx cant be installed in this computer. The disc required that Mac OS X 10.5 or later already be installed on your computer." Please help me as I don't know what to do with this.