I did exactly as you said. I did a custom action executable with synchronous (wait for execution). I set it to start in ProgramFilesFolder. The command line was:
"Microsoft Office\Office10\Outlook.exe"
(with quotes)
The command line is definetly valid and executable on the target machine. To test this I opened a command prompt, cd'd into C:\Program files and at the prompt, typed the above command, which worked, i.e., Outlook started.
C:\Program Files>"Microsoft Office\Office10\Outlook.exe"
Unfortunately the .msi still fails with error 1721. Here is the error message:
Error 1721. There is a problem with this Windows Installer package. A program required for this install to complete could not be run. Contact your upport personnel or package vendor.
This is really frustrating, because I know the program is in place.
Thanks,
Trent