Edit: Never mind my previous question.
I think LOTRO can be installed in different directories, depending on the method you use to download it (e.g. from the Turbine web site, or through Steam). If you downloaded it from the Turbine web site, the default location is
(64-bit Windows) C:\Program Files (x86)\Turbine\The Lord of the Rings Online
(32-bit Windows) C:\Program Files\Turbine\The Lord of the Rings Online
Not sure if having the extra "Erorlingas Revisted 7.5" folder makes a difference, but you should eliminate the extra nested folder.
I'm also not sure why the game would not be able to find your plugins directory. One thing you might try: Run cmd.exe, and type "set". It should show a bunch of variables. What is the value of your USERPROFILE variable?