Unable to install Ubuntu on Toshiba Sattelite after download interrupted

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http://askubuntu.com – While trying to replace vista on my laptop with Ubuntu via a boot disk, someone unplugged the computer and the installation was interrupted. I tried shutting down the PC and restarting, but found that not only was the PC giving me the "no OS" screen, but refused to load any Ubuntu disks. Is there anything I can do to re-install Ubuntu? (HowTos)