I thought you were going to serialize it to be stored in a file, sent over a network, or something like that. For what you are doing here you can ignore what I said in my previous post because the output is not meant to be used as input later on.
If you want cin>>adam.favouriteComputer; to work you need to overload the >> operator to work with objects of type computer. Not sure that's what you want though. You will in any case have to write the code to read input to set the brand, serial_no and year_produce fields pretty much like you have done with the name and email of costumer.
1 2 3 4
cout << "Enter brand of Adam's favourite computer: ";
cind >> adam.favouriteComputer.brand;
cout << "Enter serial number of Adam's " << adam.favouriteComputer.brand << " computer: ";