Now that you mention it, I do remember the issue you were haveing. It was like Mac OS 7.5.3 - 8.1 had no problem with this, choosing different partitions. But once you chose 7.1 or less 6.0.8 you could only toggle back and forth of those, unless I booted up from an external Zip drive with 7.5 on it, then I could toggle systems again