Do not put a custom ui inside either the UI\Default or the \saved customizations folder. If you want the InfoCenter and you don't have any other mods installed then you need to create a new custom folder inside the UI folder. For example:
UI\Custom
Having said that, you should really consider either installing a complete set first or in the least the EQ2MAP so that the custom folder will be created for you. Otherwise you will also need to create an eq2.ini file and set it to point to your custom folder.
Read the following for more detailed instructions (FYI, these instructions assume that you have EQ2MAP installed):
Click Here
You should also read the following before doing anything at all in regards to a custom UI:
Click Here