I am using a windows 7 machine to play a game, among other things, which was running smoothly for years, up until now. It's not a big problem but sometimes I notice drops in fps from 60 to 40 for a couple seconds which is unacceptable having in mind the machine parameters and the game's requirements (plus, as I said, the game was running at 60 fps for years).
I am not sure if that is the cause of it but when I open the task manager I notice that there is a difference between the reported memory usage and the actual sum of the processes' used memory, see below.
When I sum the memory usage manually I get something like 1800MB, say 2GB, however the Performance tab is reporting a usage of 3.1GB?
What is the cause of this, and how can I diagnose the problem? I would really like to avoid having to re-install windows because there is quite some software that I'm using on that machine and I've done my best to keep it clean with that exact idea in mind - to not have to reinstall.