It is possible that the reason the keyboard didnt work the first time is that the drivers were being installed for all the bits in the new computer before the machine could use the keyboard (ie the keyboard drivers were not in place at the point when you turned it off). It can take a few minutes for a transferred hard drive to work - if if is going to work at all!.
If you had important data on your drive then try installing it into the original machine and see if you can access it.
If I understand you correctly, you can still see things happen on your new build until the Hard drive takes over (can you see a "Splash" screen showing the motherboard or graphics card manufacturer? With the hard drive removed, try starting the machine. Do yo get a message sying no bootable devices are found? - or is the screen blank?