<p>We've got an application we'd like our users to download.  Currently they click a link and download the EXE.  What we'd like to do is have a launchpad/downloader application that would be small and fast to download, which would then download and install the main application.</p>

<p>In a perfect world the downloader would be a MSI (so we could modify some MSI databases).</p>

<p>I'm a seriosu MSi newbie, so I've got no real ideas on where ot even start looking.  Any help or pointers woudl be much appreciated!</p>

<p>Thanks</p>

<p>Andy</p>

You'll need to write a bootstrap EXE, there's a little bit of documentation in
Windows Installer SDK
or if you're wanting to take the lazy route, it looks like
MSI Factory
includes WiX compatibility and a customizable bootstrap EXE including HTTP download options.
Alternatively if you're sticking to Open-Source, checkout ClickThrough in WiX. Doesn't seem to be much info on the WiX site, so I'm guessing it's part of WiX 3. But the description sounds similar to what you need.