Microsoft used to offer a helpfile named msi.chm with lots of info about Windows Installer and MSI files. Officially they have stopped offering it in this format. They refer to online docu and files in a new format, that Windows XP cannot display. But Microsoft included msi.chm in their freely available WiX, which can be found on wix.sourceforge.net.
keywords: MSI, helpfile, msi.chm, msi.hlp