InstallAware

I want to create an installer which has two different instances:
1. Don't include .NET (to be smaller and faster to download)
2. Include .NET (for old PC's)
My project consists of a lot of files and directories, so to make two different installprojects is not very appealing. Is there any sample project or plugin which could support the make of both outputs?

Make .Net an Option/Feature so that they can download and install it if they like.

1. I've not found that I could make .NET an optional part, how do I do that?
2. Some of my customers (fishingboats) are located in areas with bad/non existing internet access, and will want to receive the installer on a memory stick.
So my task is to make with and without .NET, and I want to do it with only one project to manage.