Windows 7 now treats files dragged to application icons in the new apps bar as files to be “pinned” to menu of the application.
This can be useful for files you open regularly but a bit of a spoiler if your used to dragging image files to the Photoshop icon to open them.
The good news is that this fuctionality is still available – you just need to make sure you press the shift key whilst dragging the file to the icon and they will then open in the usual way.
Stephen