I bought this a few days ago because while I already own a copy of it I like not having to dig for my discs when I wish to install. I was wondering if there is a way to make the game work off of a thumbdrive because I would like to play while at work. However, whenever I try and run the .exe it gives me a "Your CD key is invalid. You will need to reinstall the game and enter your CD key to fix this problem." message. Does anyone have any ideas on what I could do?

If you have a CDKEY from Gog you could probably run ut2k4 from the usb drive, start the game, and type the key in the enter key menu option. But i dont know if the game can be installed in the usb drive. Maybe a rip-like installation.

Well the game runs fine on my computer at home. I copied the files to the thumbdrive and when I try and run the .exe off the thumbdrive it immediately gives me the error with no chance to enter a CD key. Are you suggesting that I try that when I get home, THEN copy the files over to the thumbdrive?

Yeah, you could try that. Install the game normally in your computer at home. Then, select all the files in the installation, and copy them to a folder created on your usb drive, making a sort of "live" installation of ut2k4, like a linux live CD. It could work.

Unreal Tournament 2004 stores its CD Key in the windows registry. That's why you can't copy it on the fly, you have to export HK_LOCAL_MACHINE > SOFTWARE > Unreal Technology > UT2004.

Could I copy that onto every computer I plan on playing the game on and have the game work? It can't hurt to try at any rate, next time I remember I'll try that.

Dont know if youll be able to edit the registry in a computer you dont have administrator privileges.

Yep, you do a right click on the correct folder on the registry (which is here UT2004), and you click on export.
Then, like drmlessgames (?) said, you have to have administrator privilegies to export and import (double click on the exported .reg) to the registry. It costs nothing to try like you said :)

If your profile has sufficient rights on the Windows registry and you know your cd key, you can attempt to use this application.
http://majorgeeks.com/Unreal_Tournament_2004_CD_Key_Changer_d4178.html
I'd advise using this also.
http://ut2004.elmuerte.com/caveo%20cavere%20cavi%20cautum

BTW, to the OP, did you get your own CDKEY from GOG? Not the generic key given to everyone that buys utk24 here, but a unique one.
You could try as well booting the computer off with a linux Live CD with ut2k4 installed on it, or with a usb thumbdrive with a linux live installation on it, and play ut2k4 from there. When youre done playing, reboot. : D

I think he may want access to the programs that are already on the computer..

Oh yeah, then, he could try a VM. : )

You don't need a CD key for UT2004 if you get it off GOG. Unless you want a unique one.

this has been told, through out the thread, already.

Yes, exactly. But if you read the OP posting, he wants to play ut2k4 on a computer he doenst have admin privilegies, and in order to play GOG's release of ut2k4, the installation program needs to copy the generic GOG cdkey to the registry, and the program can't do that without admin privilegies.