I bought a used macbook pro late 2008. 15" with dual HDD and no CD. It came with OS X El Capitan. Being this is my first Mac I wanted to wipe everything and perform a fresh install. I did so however now I am unable to reinstall the OS. It says temporarily unavailable... I tried the USB boot route but it gets about halfway through install then I get the circle with line through it.... How do I fix this?