title: System-wide Ad Blocker
body: <p>I intend to build an Ad Blocker application that blocks ads on all browsers.
  Some Ad Blockers have plugins for each browser, but I think that's a lot of work and incompatibilities. I'm thinking on an application that works like a firewall for ads.
  The main OS is Windows, of course. </p>
  
  <p>Is possible to write something that works on all Windows versions (2000, XP, VISTA, 7) ?
  What is the best approach for this kind of software ?</p>