Software Deployment

I have a couple of titles that come with MSIs on the CD, but upon launch say that they cannot be run directly and instead need to be run from setup.exe

Can someone explain what the point of this is, and if there's any way around it, like supplying a switch to msiexec. The ISScript.msi is also supplied, I'm not sure what this does, but I've seen it before.

The MSIs have been created in Installshield.

I don't want to repacakge the setup.exe because that would in effect mean repackaging the MSIs, which apparently isn't a good idea?

thanks

Michael