You can purchase the King’s Quest games for a great price at GOG.com, and then you’ll have a legal copy and won’t have to worry about spyware and viruses.
GOG is a great source not just for many classic games, but also for modern titles as well. All of the games you can purchase on GOG are DRM-free.
Unfortunately, they don’t have the Laura Bow series yet, but they do have King’s Quest.
GOG has split the series into three collections, 1-3, 4-6, and 7-8 (Mask):