Viruses, parasites, and other malware, such as the "Conficker" worm, can use the Windows "Autorun" function to infect other computers.  Autorun automatically launches a designated program as soon as you insert a CD or flash drive, or other external media.

• Note:  After you disable Autorun, installation discs will no longer automatically launch when you put them in the drive; nor will Windows volunteer to do anything with flash drives when you plug them in. 
  • To install software from disc, you'll have to manually open "Computer", and then open the disc.  Find an applicaton file named something like "Setup" and double-click it to launch the installation.

You can disable the Autorun function with the following small file:

Disable-Autorun.zip

1. Click on the above file link to display an Open or Download dialog box
2. If the dialog box contains an Open option, select it and click to proceed. 
• Otherwise:
  • Download file to your Desktop
  • On your Desktop, open "Disable-Autorun.zip" (usually a double-click)
• A "Disable-Autorun" zip folder window opens, containing "Disable-Autorun.reg", with a green and white icon.
3. Open "Disable-Autorun.reg" (again, usually a double-click) to merge it into your Windows Registry.
4. Close the "Disable-Autorun" folder window.
5. You may delete the Disable-Autorun zip file afterwards.

(I packaged "Disable-Autorun.reg" in a .zip file because some systems change the file name extension of .reg files to .mp3 upon download.)

Disable-Autorun.reg is a standard-format registry merge file, containing this text:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer]
   "HonorAutoRunSetting"=dword:00000001
   "NoDriveTypeAutoRun"=dword:000000ff

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\IniFileMapping\Autorun.inf]
   @="@SYS:DoesNotExist"
 

This assumes your Windows system has been installing Automatic Updates at least monthly, and therefore already has Update 950582 or 967715.

Please see these references, which include other ways of disabling Autorun:

• How to disable the Autorun functionality in Windows -- Microsoft
• Microsoft Windows Does Not Disable AutoRun Properly -- US-CERT
• How to disable AutoPlay/AutoRun in Windows XP/Vista -- The PC Informant
• How do I really disable auto-play in Windows XP?  -- Ask Leo