Success At Last!
With a LOT of tech support and a house call from Dr. Bob the new computer is finally up and running. I had to buy a new power supply for quite a bit more than I expected, the TV adaptor isn't initializing properly, and the CPU fan has a noisy bearing, but other than that it's all good.
Yay Bob, many thanks! Yay!
I hereby crown Bob King of all computer stuff.