AutoRun is the mechanism that proposes a default action when you insert an optical disc in the drive. For example, the contents of a file called AutoRun on the inserted CD is responsible for suggesting the action Run index.html.
Because of the rising incidence of malware that uses AutoRun to induce unwary users into running Trojan horses, the designers of Windows 7 decided to disable AutoRun capability on USB devices other than removable optical media.
Because of this security change, some devices that executed programs automatically when plugged into a Windows Vista computer might appear not to work in Windows 7. If your device seems inert when attached to your Windows 7 system, don’t assume it’s broken. Open Computer in Windows Explorer, and then open the entry for your device. You will probably find a file there called AutoRun. Opening that file in Notepad will reveal the name of the program that would run automatically had AutoRun not been disabled for your device. Run that program from Windows Explorer.