If you have an optical drive (CD or DVD) and cannot boot from it, you generally simply have to go into your BIOS and edit your boot devices or boot order. Accessing your BIOS generally consists of hitting a key (<esc>, <del> F2 or whatever, it will usually say on your first boot screen) to access what is often called your "setup."
When in your setup look for either boot order of boot devices and set it so that it will boot from your optical drive before the hard drive. This is necessary to install either Linux or Windows.
Once there, just tell Linux to take the entire hard drive and you're there.
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