InstallAware

I am using InstallAware Express 6. I just want to get my application installed with .net framework 2.0 and SQL Express 2005 SP2 right away without any hassle. I have included the Application Runtimes for "Microsoft .NET Framework 2.0" and "Microsoft SQL Server Express 2005 with Service Pack 2", but when I run the installer on a machine without SQL Server Express there is an error installing the SQL Server Express and the whole installation ends. But when i download from microsoft website and install the SQL Express separately it installs fine. Why when we install SQL Server Express separately it works but when we include it in installaware it does not? The machine is running Windows XP SP2 with the latest updates, i have tried this installer on several machines with different hardware specs also. Please help...

Make sure the installation command line is actually valid!

Thanks alot for the advice. I have disabled Mix mode and now it installes. But my problem is now when it installes SQL Express, there is no UI on the screen at all. The installer just goes blank for 15minutes or so and suddenly pop up again to resume installation. How can i over come this, as most user would try to run the installer again when actuall SQL Express is installing on the background!