If my bid is too hight to you, we could negotiate, but the final price will depend on how simple or complex is your requirement ,............. I mean , I have to know more details to take a decision...
by now, I am trying to cover all risks just in case..
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I could do it for you using inno setup, which is free. I have experience using it.
If you have the source of your current installer it is better
Only need you send my all details, all components to install, folders to use.
Please see my profile about my responsability in comments from my clients.