After installing JRiver MC19 on my Windows 7 Ultimate and Windows 8.1 Pro machines (64bit) I noticed 2 things happen on both machines:
1- Windows Media Center suddenly lost the ability to see the JPG images in my photo folders, the folders in My Pictures themselves show, but the JPG files disappeared, I could only see BMP and GIF files.
2- Windows 8.1 photo app (Metro, touch UI) also lost the ability to display photos in JPG format.
After messing about with this issue for days, I found the following registry items were flawed:
HKEY_CLASSES_ROOT
.jpeg and also .jpg had blank "Content Type" and "Percieved Type" string values
I changed Content Type to Image/Jpeg
I changed Percieved Type says Image
That fixed the issue... This happened on all machines at home where MC19 was installed..