Norton is the spawn of satan.  For some reason my idiot boss got Norton installed on all the work PCs after I left their employ only to return 10 months later (don't ask!) and on my first day back got handed a long list of problems with the PCs and asked if I could sort them to out to save paying for a tech to come in (I'm the Service Manager).  A good 90% of the reported problems disappeared when I nuked Norton of each and every PC.....the rest were down to idiots opening and evrything that plops into their Inbox sighs

Be careful when using anything that purports to clean your registry - they can completely nuke your machine if you aren't careful.