This is a question I've been trying to get my hands around for months! I really wish InstallShield would publish a white paper on it. My theory is that IDRIVER.EXE and IDRIVER2.EXE expose the exact same DCOM server but with two different entries in dcomcnfg. One to instantiate as the interactive user and one to instantiage as the launching user.
Unfortunatly you will find quiet a few threads where people are pushing with SMS 2003 using the LocalSystem account and whenever they use InstallScript it crashes on them with ROT table problems. My solution to this date has been to modify the InstallScript runtime MSI that setup.exe installs so that both instances are run as the launching user. All errors go away. Unfortunatly this has also required me to author my own DCOM server and configure it to run as the interactive user. This allows me to do certain things as the logged on user that I need to do.
Bottom line is I have a working solution, but I really wish I didn't have to do any of this. The best I can find is on custom actions there is "defferred and deffered in system context". Does this mean 1 uses IDriver and one uses IDriver2? Good theory except that custom actions don't even have to be using InstallScript.
I know several people have called IShield Tech support on this issue and the answer has varied from "oh we fixed that along time ago" to "that is the way it is designed ( without explaining the design".
