A shame but the CD key for the game that comes with it fails.

[Skkooomer Lord]

Playing it using DHEWM3 instead with Sikkmod, works fine.

[j4w4]

Same here. I'm playing the GOG version and it literally removes the key from the *doomkey* file every time I try to put it in. So, I got the `Dhewm.exe` installed and there is no nagging anymore for a key.

[GamerXT]

It asks for a key ? Never seen that I don't think.

[Lippeth]

You can bypass Doom 3 and RoE asking for the cd key by opening the console "ctrl+alt+grave accent (the key next to 1 on the number row)" and typing "disconnect" and it will let you play without needing a key, but you may have to do this every time you play, or add it to launch options or create a batch file.

As far as the key being invalid, the first thing I would try is verifying the file integrity in the game's properties. If you just want to type it in manually, making sure the letters are capitalized might help, and make sure to type the last two characters in the second field. If it's still invalid after typing it correctly, click cancel to quit the game and check in the game folder's base folder to see if a key file has generated. If so, chances are it won't ask for the key next time you open the game.

Doom 3 cd key business is weird for sure, and it seems like every so often it just wants it again. You can also right click the doomkey file in the base folder and open with a text editor to see if the actual key is there. If it isn't, you can delete the entire file and re-enter the key when next launching the game, preferably in windowed mode so you can see the key.