I hadn't heard of it until you posted and I see from a Google Search that it would appear that none of the regular antivirus applications detect it.
I would imagine that McAfee Stinger or Fake-Alert Stinger might as they are similar tools to the Norton one you used.
If not I would recommend the free version of Malwarebytes and as the last resort file a Hijackthis report on one of the specialist forums that deal with them.
All of the above are laid out on a page I put up here: https://community.mcafee.com/docs/DOC-2168
It's wise to keep some extra anti-malware applications handy and updated just in case this sort of thing happens.
Startnow.com has a poor reputation on WOT but if you look at the forums and the site page comments there's an active pro-Startnow lobby (genuine or not, I don't know). The lobbyists loudly proclaim that Startnow is nothing but a portal for Bing searches but everyone else (in dozens of forums) is complaining that this outfit is responsible for start page hijacking, browser redirections, and installing a toolbar that it's difficult to remove even after following the uninstallation procedure. According to SiteAdvisor their site is linked to zugo.com, which really does have a bad reputation.
At the very least this is an annoying PUP, but I doubt it's actually a virus. Stinger might not be helpful, but it's worth a try. I'm not even sure that Malwarebytes would deal with it, although it might. Whatever it is, it's been around (and complained about) for a couple of years at least.