When you insert a removable disk like CD or USB thumb drive, Windows starts auto play wizard. Windows searches the removable disk for its contents and suggests an appropriate action. If the removable disk has a file autorun.inf in its root folder, which is common for software and game CDs, Windows prompts to make it default action for such CDs as shown :
If you check the checkbox labeled Always do this for software and games, the action of executing autorun.inf would be made default. Next time you insert any such CD, the autorun.inf would run automatically which results in running a setup program for that software or game. The problem is that some viruses and malware use this method to run themselves and infect computers.
If you have checked the checkbox show above in past and want to reset it, so Windows does not execute autorun.inf automatically, follow the steps below :
- Open Start Menu → Control Panel
- Goto Hardware and Sound → Play CDs or other media automatically as shown in the picture below :
- In the next window, scroll down to bottom and click on the button labeled Reset all defaults on the left. Then click on the Save button on the bottom right corner.