Then the manufacturers load them with an 'operating system,' which is a program, but it won't really do anything but accept other programs. Then the owner of the computer can write his own programs, or more often load programs from disk, to do all the things he wants the computer to do. When he's done whatever he wants the program to do he can erase the program from the computer - he's still got it on disk for the next time. Brains can't do anything like that at all. But brains are different from computers, and minds from programs, in other ways.
Computers feel no hope, fear, love, or any other emotion.
They have no imagination or ideas of their own. Programs have been written to simulate some of these activities, but they're all more or less pathetic, like a child dressing up in grown-up clothes. If minds have all these faculties that programs lack, perhaps they have real free will as well, not just the pseudo-free will which is derived from random number generators. So it might be genuinely 'free' even in a completely determined world. The program runs the computer, not the other way round.