You can not be told what a MST is, you must expierence it yourself. The easiest way to make an MST, is make modifications to an MSI, compare it to the original, and voila MST file, WITH the orignal MSI to install from. Half the time, the serial numbers that are entered into the serial number fields in the MSI are typically saved in a Property, you just create the property, put your serial in there, and then the INSTALLATION registers it by it's own methods. Before subjugating saying one method is better then the others, do try it YOURSELF, and use a little logic as to why the MSTs were created to begin with, instead of instructions on how to modify the MSI directly. There are reasons.