Do you happen to use a Logitech mouse driver? If I recall from a previous system that had a cordless logitech mouse and keyboard, the em_exec is for that.
By the way. If you really want to get dirty in the registry and see things that are not in the startup folder, you can check the following registry locations. They are kind of nice because they frequently give the exact path to the executable.
Also, I don't know if this file is still valid for the more modern Windows platforms since it is a holdover from Win3x, but it did work in the 9x family. If you have a file called winstart.bat in the windows directory, it will run anything in it on startup.
So, startup folder, registry, winstart.bat, autoexec.bat, config.sys, win.ini load and run lines. All the places an application can start from