I am unclear about the System State restore. Suppose I restore the System State followed by reinstalling my other Programs (Visual Studio, etc.). In such case the registry value is updated with the new installation. So how does the System State help me here?
Restoring the system state winds the registry back to whatever it was when you did the backup, hopefully removing any registry corruption that hapopened after the backup. If you didn't have your apps installed when you did the backup then obviously restoring the system state will remove their install/config details. This may be a good thing of course, because a failed installation may be why you want to restore the system state back to an earlier version.
Like splattne I'm not sure what your question is.