MacMini stop booting after pen drive use

Hi to all. I needed to do a clean install of OS X Sierra on two Mac mini late 2014. I used the same couple of USB drive that I created to install Sierra on my Hackintosh but installation process didn't started and after this my Mac mini stopped to boot; every time I turn it on I can only get a series of beep (the same beep you can ear at the boot) repeating every two seconds and this series of beep that doesn't stop.
This happened on the same time on both Mac mini.
Does anybody can help me?
Thanks, Antonio

addendum... I trie to reset Nvram using cmd + opt +P +R but it doesn't works

Zottwalker said:

I used the same couple of USB drive that I created to install Sierra on my Hackintosh but installation process didn't started and after this my Mac mini stopped to boot

Click to expand...

See https://www.tonymacx86.com/threads/...clover-on-a-real-mac-can-be-dangerous.229629/

P1LGRIM said:

See https://www.tonymacx86.com/threads/...clover-on-a-real-mac-can-be-dangerous.229629/

Click to expand...

Thanks!