Unity 5 Legacy Files Won't Open

I recently updated to Unity 5 and I can’t access my legacy Unity files from Unity 4. They’re grayed out and won’t let me open them. When I just double click on the file, it says there is no application for that file type. However, I definitely have Unity open and running so I’m not sure how to resolve this. Please help!

The file extension .UNITYPROJ wouldn’t open. We were able to open .unity files after upgrading the project to Unity 5 and it appears that the assets are there but not displaying.