Upgrading from Windows’ built-in antivirus tools can cost a pretty penny at full price. Fortunately, you can get top-notch protection at more affordable prices if you know where to look—like PCWorld’s own software store, which currently has an exclusive deal on Norton 360 Deluxe. For just $25, you get 15 months of coverage for up to five devices. Normally, this suite — our favorite antivirus software — costs $120 for a 12-month subscription. First-time subscribers can get it for $50, but that only lasts for the first year. Norton 360 Deluxe is one of the best antivirus suites if you’re looking…