Windows issues. HELP!!!!

When ever I set a photo as my desktop background, my internet browser shrinks. Why is that? It just randomly started doing that.

Also this other issue I have been having for a while, if I have a lot of images in a file, when I scroll down to the very bottom or anywhere other than the top rows of photo and I set any photo as my background, the window scroller automatically zips to the top... why!! I have tried to find an answer on google but with no luck.. help!