Problem is, all my RAW files still open with LR4 by default and I can't change it.
Why do you say this? How are you opening your RAW files?
Is Lightroom 4 still installed on your system? Or is Lightroom 5 the only version now?
I also upgraded LR5 to 5.7 to open the D3300 files but it still can't open any RAW images. I've tried right click/ open with/ choose default / browse / Cdrive/
Lightroom has been designed to NOT allow you to open images into Lightroom via operating system actions like "Open" or "Open With". This is an intentional thing that Adobe has chosen to do. I realize that some people report that they have successfully done this in the past, but as far as I know, you are prevented from doing so by the software. The proper way to make use of RAW photos is to do File->Import in Lightroom.
LR5 is the only version now. I normally open my RAW files by going to start menu on my PC then select pictures, then open a folder and double click on a RAW file(I shoot in RAW + JPEG) They are now opening with picasa and I can't change it to LR5
That's right. That's what is supposed to happen. You can't "open" photos into Lightroom with the method you are trying.
To import the photos into Lightroom, you need to first open Lightroom and then either
- use File->Import; OR
- drag and drop the files from Windows onto the Lightroom screen