Do you need WC3:RoC once you install TFT? (CD-Key problem)?

Unfortunately, I only have the case and CD-Key for TFT, so I'm using someone else's CD-Key for RoC (both CDs were bought legitimately from stores, I just lost the RoC case and Key). Whenever I try connecting to Battle.net in TFT, it usually shows other people using the CD-Key in RoC. Is there any way to cirvent this? Please don't suggest I buy a separate RoC CD-Key. That's not happening.