Your best bet may be to "Unload WB via the system tray icon context menu (or config panel) > go to Display Properties\Themes tab > select Windows XP in Theme drop-down list > click "Apply" - all before shutting down machine.

If I am not mistaken, the WB version 5 uses both ".dll" files and registry keys to apply and load skins to modify the explorer shell (similar in some respects to the "Themes" service included with Windows XP). Therefore, we have 3 options for viewing the explorer shell:

1 - the native Windows GUI (Classic) with no theme.

2 - the built in "Themes" service to apply "Luna"

3 - WindowBlinds 5, which basically modifies the native Windows GUI, instead of the "Themes" service. Thus, when you unload WB, you end up with the Classic look, and must reapply the "Luna" theme to tell Windows to use the built in service. Without telling Windows which service or theme to use, it will use the previous settings on reboot.

I do not code, nor work for Stardock, so I can not relay any keys you can modify to enable the result you seek. It would probably be inappropriate to relay such information anyway, due to possible issues that may result.