procedure Abort;
Escapes from the current execution path without reporting an error.
Abort raises a special "silent exception" which operates like any other exception, but does not display an error message to the end user.
Abort does not cause Setup or Uninstall to exit unless it's called from one of these event functions (or another function invoked by them):
InitializeSetup
InitializeWizard
CurStepChanged(ssInstall)
InitializeUninstall
CurUninstallStepChanged(usAppMutexCheck)
CurUninstallStepChanged(usUninstall)