I'm confused. I bought a Dell Precision 3420 Small Form Factor Desktop Workstation with Windows 10 Pro pre-installed. Before booting up for the first time, I installed a 3rd party graphics card (Radeon 7750 with 4x mini DP). Then, I attempted to boot into a disk cloning software so I could replace the stock 1TB spindle drive with an SSD. At first, I had to use the integrated video, as the 7750 wasn't being recognized. In the Dell BIOS there is a video selector and it was set to Auto, but it defaulted to the integrated graphics (Intel HD 630), however I was able to choose the Radeon to be the default and when it rebooted, it picked up the signal from the Radeon and everything seemed to be fine.
After the disk cloning, I attempted to boot Windows 10 and no video. In fact, the fan on the Radeon isn't even spinning, as if there is no power to the card. I connected my monitor to the integrated graphics and it came right up. I went back into BIOS and the Radeon choice is gone - only Auto and Intel.
I started all over, with a different SSD, and everything went just like it did the first time. As soon as I tried to boot windows, the Radeon stopped working completely. Within Windows, there is no indication whatsoever that WIndows sees the Radeon. It is not present in Device Manager or other hardware identifiers.
Anyway, I assume I am missing something, but I haven't been able to find it on my own, so I beg you all for help. I am emotionally prepared for the reality that I cannot use my neato Radeon card in this system, but I haven't given up hope yet.