Q: Can not install OSX on Mac Pro 5.1

I just got a Mac Pro 5.1. I wanted to just move my current drive from a Mac Pro 4.1 over as well as the video card. I did and it booted at first, then it asked me to download an nVideo Cuda driver. I did and have never been able to get it to boot again. . In addition to that, when I hold down the option key while booting, I get a screen with a locked lock and a window asking for a password. Keep in mind that I just bought this computer with no drive at all, no video card and no ram.  I have since added a blank SSD, 24 gigs of ram from DATA MEMORY SYSTEMS and put in a Mac nVideo GeForce GT 120. I have tried entering all kinds of passwords, none work,  But why would I need a password to get to the boot select screen by holding down the option key?? It won't boot from DVD either, the disc spins, but I just get the blinking folder icon with a question mark.