You cannot take a hard drive with an OS installed on it and move it from computer to computer and expect it to work. It will work sometimes if both systems are very, very close to exactly the same. But even then it is a long process to get everything going, and it still can be very buggy. Trying to go from a desktop to laptop is a big FAIL. It simply does not work that way.
What you should have done is exactly the opposite. Take your notebook hard drive and install it as secondary drive in your still working computer.
I would not be surprised if you find when you put your main drive back into your desktop now, it won't boot there any longer either.