Yea that sounds about normal. It should "lock" the entire machine per say that you have to reboot, but it will stay at points where it would say maybe "deep scanning local registry" for a period of time. Espcially on a full system scan it has a lot more items to scan. So long as it finishes and you see and hear the little red bug (dang it always scares the crap out of me when I have the speakers loud..lol).