Fun.exe is an e-mail attachment virus.
The virus will install multiple copies of itself throughout the system. It makes itself hard to remove by installing many different copies with different names in different locations. The running copy is a system process and will restart if it is closed manually. It adds itself to autorun information so that it executes multiple copies on startup. The copies monitor each other and will restore each other if one is deleted. This makes manually deleting it from Windows nearly impossible.
The file icon is made to look like the icon for a folder, inviting the user to open the folder when actually they are running the program thus starting the initial infection. However, the graphic icon for the folder is poorly ripped from windows service icons and can be distinguished by subtle visual differences, predominantly white below the black outline of the folder which on the real folder icon is dithered to transparent space. This visual difference is especially noticeable in safe mode when graphic operating capacity is in 256 colour mode instead of 24-bit colour mode.