WIN.COM is the executable file used to load versions of Windows

Microsoft Windows

Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

 that run from DOS

DOS

DOS, short for "Disk Operating System", is an acronym for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition.Related...

. In Windows 3.1 and its predecessors, it is executed either manually from the DOS prompt or as a line in AUTOEXEC.BAT

AUTOEXEC.BAT

AUTOEXEC.BAT is a system file found originally on DOS-type operating systems. It is a plain-text batch file that is located in the root directory of the boot device...

. In Windows 95 and onward it is automatically invoked by IO.SYS

IO.SYS

IO.SYS is an essential part of MS-DOS and Windows 9x. It contains the default MS-DOS device drivers and the DOS initialization program.- Boot sequence :...

 after AUTOEXEC.BAT is processed. The file is present in the SYSTEM32 folder of some NT-based versions of Windows (such as XP and Vista) for backwards compatibility purposes.

Usage

WIN.COM has several parameters that facilitate system recovery and diagnostics. These parameters are listed on this Microsoft

Microsoft

Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...

support page: http://support.microsoft.com/kb/142544.

Issues

Corruption or deletion of WIN.COM caused many issues for users of Windows 95 and 98, and some early Windows viruses targeted WIN.COM. Corruption of WIN.COM would cause an error, and a Microsoft support page is still available showing information about WIN.COM errors.