I, too, had the problem of the Windows Installer popping up every time I tried to run any of the EMC8 programs, and discovered a solution to my problem.
First, a little background: I originally purchased the download version of EMC8 in December of 2005. At the time I was running Windows XP Home. I had all current MS updates installed.
Fastforward to today: I rebuilt my computer with Windows XP Pro SP2. I installed all current updates.
And therein lay the problem.
I followed many of the suggested solutions in this forum and now list them below:
Installed Windows Installer Clean Up utility, found here:
Be sure to remove all Roxio and Sonic entries.
Manually deleted folders containing the Roxio and Sonic software, including the folders located at Program Files\Common Files\<ROXIO/SONIC> Shared\
Download and run REGSEEKER, removing all entries related to Roxio and Sonic, as pertain to EMC8. Repeat as necessary.
Go to Control Panel\Add or Remove Programs. Find and uninstall Windows Installer 3.1. (This will reinstall automatically the next time you go to Windows Update.)
After the reboot, install EMC8. Run the programs at least once (it may ask to install one time and reboot, but I don't recall exactly).
This is the only thing that worked for me. You MIGHT be able to just uninstall EMC8 normally, uninstall Windows Installer 3.1, and reinstall EMC8.
Let me know if this helps!