Consistenly getting Block magic mismatch error?
You have a corrupted block file. You will need to delete that file and all higher number files and then redownload the entire blockchain.

The block file that is corrupted is the 0th file, blk0000.dat. Since this is the first block file that Bitcoin Core creates, the easiest thing for you to do is to just delete the entire blocks and chainstate folders in your Bitcoin Core datadir. Then start Bitcoin Core. It will redownload the entire Bitcoin blockchain.