[Coder-san]

Explanation

By Default in Windows, Autoplay is turned on for whatever reason it is made (however I do not know many people who use it).

What harm it can do?

• Autoplay is used by USB spreading (or Autorun.inf spreading) malwares to infect the host computer the USB drive is plugged in.
  
• Autoplay allows applications to run when a USB drive is plugged in, slowing down your PC (And slows down even more if you have a realtime-AV).
  

Solution

Turn off Autoplay, we don't need it. If you do for some outlandish reason, enable it back again.

1. Open Run and enter gpedit.msc
   
2. Go to Computer Configuration.
   
3. Go to Administrative Templates.
   
4. Go to All Settings, in case of Windows XP go to System
   
5. Search for and double-click Turn off Autoplay
   
6. Choose Enabled and Turn off Autplay on All drives. Like in the image displayed below.
   
   
7. Now go to User configration and repeat 3-6

You just disabled Autoplay, and you can plug in random USB drives without the fear of getting infected.