Im not good with English, could somebody help me to find the CDKEY, I just bought Unreal Tournament 2004 ECE and I dont know where I can get the CDKEY... Thanks .

The CD key is stored in the registry. You can find it here:

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Unreal Technology\Installed Apps\UT2004]

The key name is CDKey and will contain the default key from GOG's installer. If you raise a request to GOG support they will provide you with your unique key and you can just replace the contents of this registry entry with your unique one once GOG send it to you.

Thanks, I try to contact support but they havent replay me :(

I searched for the Gog UT2004 CD key to install the Linux client and your tips helped me to obtain it, thank you.

this method do not seem to work anymore.