Changing Folder Pictures In Windows Vista

I am sorting my music out on my PC (I've had a new one).

So I want to change the folder picture in my music albums to the album cover.

I have right clicked on the folder, clicked customize, clicked 'choose file' under folder pictures, and clicked on the image I want, but nothing happens. It doesn't appear as the thumbnail.

I have also just added the picture in the music folder, and I expected Windows to automatically detect the image and use it as the thumbnail, but that hasn't worked either.

It is doing my head in, any advice? I have been to control panel and checked the folder options, and all seems correct.