My name is***** will help you too the best of my ability.
I'm sorry, to say that I don't fully, understand your logic here. If you have one SATA Port it's good for one drive, IDE allows for two drives on the same cable. You can only add as many drives as there are SATA Port connections.
It's good if you have important data, backed up just in case one should fail. I don't understand what you are refering too by it's generation errors you will need bigger then a*****too hold 1.5 terra files. Any rate, you can proceed either way with mounting the drive long as there is slots too put it.
You need more then a terra worth of space since there is a additional, 500 GB. If the machine also, has the space you can have as many additional, drives as you want