Hi Wort - I use it and can confirm that it is Windows compatible. CPU usage is usually at no more than 1%. It works with Windows Vista and Norton security with no problem or conflicts at all. The reason I use it is that it provides me with protection when I game online (and take down Norton and my firewall). Also, I find that because it relies on real-time behavioural analysis, it spots problems and deals with them before Norton picks up on them. I've not had any roblems with it - had it since the end of April 2008. I think it is a white label provided by Sana Security (the Tiscali proice works out cheaper but you still get the latest version). Hope this helps.