That's pretty much what I was trying to say. :) Except that there are also the memory mapped files (your user32.dll example). afaik if an app loads a DLL it is mapped into that app's address space, but the DLL's code is not copied into the physical or virtual memory, instead the space the DLL takes up on the harddrive becomes part of the app's memory. You could probably compare it to the swap file, except that it's read only. Some of it might be copied over if it's frequently used. What I mean is that if multiple apps load a DLL the "memory usage" task manager reports will increase, but "real" memory consumption doesn't go up. That's how it was explained to me anyway. :p