Even though I know nothing about how these server files work, even I can see how stupid this 'problem' is.
You are comparing 2 things.
#1 : A hexed mainserver where you indicate "skill.dll".
#2 : A client with an error that it can't find skill.dll
First of all I highly doubt that the way you hex your mainserver has ANYTHING to do with an error you get when you startup your CLIENT.
Why? Because you are only starting up a client, it is not even connecting to a server yet, it's in the stage of loading the data files.
Now you expect your client to work by putting 'cskill.dll' inside your client folder?
Anyone with a little bit of common sense knows it doesn't work that way.
If your client searches for 'skill.dll', you need to provide a 'skill.dll'.
A comparison: Let's say you get pulled off the road by a police officer and he asks for your driver's license, you are expected to give him a driver's license, not a shopping list or something.
Your client works the same way. It requests data from skill.dll which clearly doesn't exist in your folder, so it will generate an error.