There should only be one Client.ext in the Neocron 2.2 CE root directory, it will have the orange Neocron logo.
The only other executable files in the root directory are neocron2-uninstall.exe, NeocronLauncher.exe and nlsp.exe.
It might be worth installing Neocron again but name it say Neocrontest and put this directly in your C: or drive i.e C:\neocrontest, that way you have a normal version and a modified one. Then run the launcher, setup the graphics settings and launch the game to patch it. Once done and everything is pre cached try the above fix and run the client.exe .
Hope that helps!