Dr.Windows is a small and funny program that adds an icon in the system tray apparently protecting your system as a security program, but it is actually a joke program.
It periodically displays pop-up joke messages as if they were system alerts (e.g. "Windows has detected that you have moved your mouse. Please restart your computer", or "Error detected"), but indeed nothing happens on your computer, and if you press any button from the alert, the message window is just closed.
The program includes 56 joke messages in total which can be shown randomly. You can set the period of time to show the messages and set a shortcut key to activate a message instantly.
The program also gives you the option to add your own personalized messages, but it has to be done with a third-party program.
You must be wondering why to install a program that has nothing more interesting to do than bother users. Well, there is an advantage; some distraction may give users the chance to take a break and have a relaxing time.