Windows Installer XML (WiX) toolset is an open source project that enables developers to build MSI packages based on XML definitions of MSI tables.
Early versions of the MSI Wrapper depended on the WiX toolset but this is not the case anymore.
Now you just download the free version and wrap your installer.
If you are interested in the WiX toolset then you can download it here. Using WiX requires in depth knowledge of MSI packages.
Get the current stable release here