http://www.west-wind.com/WebLog/posts/240.aspx

“If you’ve ever run your app and looked at Task Manager you might have noticed that the app starts out with a significant amount of memory. A basic WinForm app with a couple of textboxes and a button typically will run around 8 megs. If you move the form around a bit closer to 10. You then can minimize the app and it generally reduces to some really low memory usage number which slowly creeps back up as you open the form back up. What’s happening is that the app internally is adjusting the Working Set for the application which aggressively reduces the memory in use by the app. The app will reclaim what it needs, but for that moment the memory usage goes down drastically and it will stay much lower than the original startup usage.”