The difference between “turn off” and “shut down” in Windows 7 version of Virtual PC

Configuration Description

OptIn This setting is the default configuration. On systems with processors that can implement hardware-enforced DEP, DEP is enabled by default for limited system binaries and programs that "opt-in." With this option, only Windows system binaries are covered by DEP by default.

OptOut DEP is enabled by default for all processes. You can manually create a list of specific programs that do not have DEP applied by using the System dialog box in Control Panel. Information technology (IT) professionals can use the Application Compatibility Toolkit to "opt-out" one or more programs from DEP protection. System compatibility fixes, or shims, for DEP do take effect.

AlwaysOn This setting provides full DEP coverage for the whole system. All processes always run with DEP applied. The exceptions list to exempt specific programs from DEP protection is not available. System compatibility fixes for DEP do not take effect. Programs that have been opted-out by using the Application Compatibility Toolkit run with DEP applied.

AlwaysOff This setting does not provide any DEP coverage for any part of the system, regardless of hardware DEP support. The processor does not run in PAE mode unless the /PAE option is present in the Boot.ini file.

you are correct in what your gut tells you.