1. Reinstall WC3 (Both RoC and the TFT expansion pack). This is to make sure your installation is correct.
2. Update WC3 to the lattest patched version (usually by logging into battlenet). This is to make sure you are up to date with everyone.
3. The editor should now boot (as a patched removed the need for the CD to be present to start). This is because they made a virtual distribution of the game so a disc might not be available.
Diablo II, WC3, WoW, SC1 and SC2 all do not require a game disc be present inorder for them to start. This is due to them being available for virtual distribution.
The message asking for a CD can still appear but that usually is a result of some other error.