Microsoft Compiled HTML Help is a proprietary format for online help files, developed by Microsoft and first released in 1997 as a successor to the Microsoft WinHelp format. It was first introduced with the release of Windows 98, and is still supported and distributed through Windows XP and Vista platforms.
html help files are made with help authoring tools. Microsoft ships the Help Workshop with supported versions of Microsoft Windows and makes the tool available for free download. There are also a lot of third-party help authoring tools available.
The Microsoft Reader .LIT file format is basically a modification of the HTML Help CHM format.
In 2002, Microsoft announced some security risks associated with the .CHM format, as well as some security bulletins and patches [1]. They have since announced their intentions not to develop the .CHM format further, and will be moving to a new generation of Windows Help called Microsoft Assistance Markup Language in the Windows Vista operating system.
Here you can find a list of chm file creators:
1. WINCHM
2. Visual CHM
3. CHM Maker
4. Pocket CHM
5. Abee CHM Maker