hikaru.exe, mostly known as the Ghost virus or the Sadako virus in Japan, is a japanese screamer joke application. It is a variant of the Win32.Joke_Ghost joke program. If you run it, it doesn't seem to do anything, however it silently becomes present in the operating computer's memory and triggers a payload at random times which shows a full-screen picture of a ghost girl, similar to McDonalds.exe, but not the same with a scream sound effect. It quickly spread over the Internet in Japan in the early 2000s, like McDonalds.exe. However, it didn't become as popular as its cousin. Some have complained that even when restarting the computer, the screamer will continue to pop up normally.
A similar version of this application exists, called madoka.exe. Both programs seem to do the same things, but they have a different screamer picture.
NOTE: The following video contains a screamer.
NOTE: This program could potentially harm your computer.