As I've said, there's nothing wrong in the registry that might "confuse" Couatl, the problem is surely caused by some other addon. The only thing that are "left" in the registry, it's your Serial Number, but that can't possibly create that issue, since it's stored in each user profile just the same so, fact that is running in the other user account, clearly proves is not the registry the problem.
No other registry keys are used by Couatl, except that is reads the keys created by FSX, to know where it's located.
First, the list of process is not the only thing that is running, there's also the list of services. You should also check processess and services created by all users, not just yourself, there's an option in Task manager for that.
And, you can also use the msconfig program to enable/disable startup processes. Type "msconfig" at a command prompt.