Are you certain that it is Express Dictate which is starting up? I checked our test system here and it wasn't set to startup by default. If it is one of our other programs then you can tell it no to start via that option I described earlier.
For a solution: have a look at your start menu startup items, and if you're comfortable with the Windows registry (regedit), have a look at HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\ and HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\.