In my (considerable) experience, as I sort them out when they're broke, NIS is OK but it does slow any system down considerably. The latest version 2007 is worst of all. I recommend, as have others, using freeware, such as ZoneAlarm for a firewall, AdAware and Spybot S&D together and run both weekly. Set a scheduled diskcleanUp to run automatically every day and make sure that you also install Windows Defender from the Microsoft site. If you run all theses properly updating them before each scan, you PC should remain free. Also make sure your Windows Updates are fully up to date, set your PC to Autoupdates, but make sure that you click "Custom" when you check, only this way will you get all your driver updates as well. For Antivirus use AVG Free. All are available from various sites, but try ww.computeractive.co.uk/downloads. You must use common senseabout what emails you open as well. The golden rule is "if you don't know who it is from, don't open it". This way you should stay clean. I know believe me!!