If you read the myriad of posts that you can access via the 'SEARCH' function, you will learn at least two things:
You must follow the instructions.
REP does not work for everyone. (I personally could never adjust the water textures to my liking.)
You just choose your dawn,dusk,night,clouds,water textures. Then go to main and hit install. Thats all you should do.
Mine didn't even install properly so I had to look for a folder named "install" that's located in your real environment pro folder after you install the software. It should be found under the Program Files folder on your driver.
I copied the new textures manually and now it works the same.
I use different water, ground and tree textures so I don't have to constantly be changing back. But you will have to if you like all of the REP textures
Hope that helps!
I think I'll just stick to 'original', and never have problems.