AutoRun and the companion feature AutoPlay are components of the Microsoft Windows operating system that dictate what actions the system takes when a drive is mounted. AutoRun was introduced in Windows 95 to ease application installation for non-technical users and reduce the cost of software support calls. When an appropriately configured CD-ROM is inserted into a CD-ROM drive, Windows detects the arrival and checks the contents for a special file containing a set of instructions. For a CD containing software, these instructions normally initiate installation of the software from the CD-ROM onto the hard drive. To maximise the likelihood of installation success, AutoRun also acts when the drive is accessed ("double-clicked") in Windows Explorer (or "My Computer").