Chose USB from boot menu, PC went to this and got stuck.

I have HP Compaq 8200 Elite SFF, with i5-2400 and Nvidia Quadro K620. I followed the dortania guide the best I could, though there were some inconsistencies (probably typical, right?). Anyway like I said I followed the guide to the best of my ability, and now trying to boot it's just stuck on the first message.