Darkenmal: Just bought Unreal Tournament 04... and the installer says that the files is corrupted. Can someone from GOG fix this plz?
Also: How do I get another CD key for this game so I can go online?
Re-download the files. If you downloaded via browser, try the GOG downloader, if you used the downloader, try from the browser. It can happen sometimes if there was any interruption in the download (even just momentarily). I have the setup files and they work fine, and I wouldn't expect GOG to just change the files on their server unless they had to make a fix, which as far as I can tell from the forums they've not had any need to do.
As for the CD key, have you read the GOG terms and conditions? Provided you have purchased the game from them you can send them a support request to ask for one.