I would recommend a good text editor, if you are using notepad do yourself a favor and change to just about anything else!
I maintain a list of some very good and free Windows text editors at "http://dennisbareis.com/bookmark_windowstexteditors.htm". I use "JEDIT" as it is multiplatform (works in Linux), free, and has many extensions, some specific details about some of these editors are:
The "PPWIZARD" home page has some information about PPWIZARD syntax highlighting, it should not be difficult to improve this to include MAKEMSI. If you would like to contribute any you create/update yourself then I can post the information or link to your site to make this available to others.