Hi art, yes like Brian mentions above for v4 you should install it into the appdata folder, not into \Program Files.

Install instructions are here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=6507.268

Try using Win+R to bring up the Windows "Run" dialog, and then type in:

%AppData%\Moi

and push Enter. That will open up the MoI appdata folder.

When you unzip CustomUI.2.0.beta2.zip there should be 3 folders that were inside the .zip . The folders are "customui", "objects", and "startup".

These should be copied over to the %AppData%\Moi folder.

So you should end up with:

%AppData%\Moi\customui
%AppData%\Moi\objects

and there will already be a %AppData%\Moi\startup folder, copy the contents of the startup folder in the .zip file into the %AppData%\Moi\startup folder.

- Michael