All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
Copying and buying copied copyright CDs is a kind of transgressing other people's money without right because these intellectual works became in a point of view of customs and reality monetary rights of its owners, so it is not permissible to do anything with them without the prior permission of their owners. However, this does not mean that doing so is a kind of real theft, because Islamicly theft has its definition which is different from the above.
Therefore, whoever copied or bought copied CDs while knowing that they are forbidden, is obliged to repent and be determined not to return to that again. However, if one has done so while not knowing the ruling then he is not sinful and he may personally benefit from the CDs which he has but he should not sell them to others.
For more benefit, please refer to Fatwa 82653 and 85102.
Allaah Knows best.