When you purchases a used EQ, ask how many times it has been installed. The older version could only be installed 3 times. But, I think they have changed some of that. The person you are purchasing it from has to take it off their computer and call or email the company and give them the serial # and your name, then you can put it on your computer and even purchases upgrades as they come out. Also, if you have the serial #, you can call the company and see how many upgrades are left. If it goes on the same computer, I don't think it uses up your installments. But, check as they had changed a lot of things in the last few months.
Virginia in TX