Windows Installer… nightmare… WISE – hurt me plenty. Although this is much simpler and logical to my mind then WI it is still very sensible to changes. What I am trying to say – if do everything right from the first time e.g. correctly choose all names and dialogs and files e.t.c it works perfectly. But when after 5 minutes you decide to change, say, some script or file destination WISE i making so many actions in background you can’t even imagine. This is because of many assumptions WISE makes upon what actually you are trying to do. So the bad part of this is something won’t just work even if looks the same as before.
So my advise is: to backups as often as you can. Done an action – it is working – save this version and only than continue. Otherwise you’ll have hours of figuring out why this or that happens and than be much more surprised with everything working again if you start everything up from the beginning. Happy installation making!