Install Mods for Unreal Tournament 2004
Install the UT2kx Reg Checker tool and you can happily double-click to install your mods.
If somehow this doesn't help, then as a last resort you can re-install Patch 3369. This will reconfigure the bindings so that your *.ut4mod files should work again.
First of all, are the .ut4mod files associated with UT2k4 so that Windows knows to use that program to open them? Or do you want to run the mods without needing to install original client?
If they're already associated, have you tried rightclicking on the files and choosing "Run As Administrator"? With several .exe's I've downloaded from various sources for various programs, sometimes things just don't want to play nicely in Win 7. The first thing I try if things aren't installing nicely (I'm on Win 7 Ultimate) is Run As Administrator.
Finally, if that doesn't work, I would check out this page, as it has a bunch of UMOD troubleshooting tips. Good luck!
I would put the mods into the Unreal Tournament base folder, the one that stats system on it because I remember having the same problem with installing a mod for Star Wars: Jedi Academy. What I did to fix it was to extract and move the files into C:\game folder\jediacademy\data\base
and then when you load the game it will load the base files.