Windows: Disable caching of large files

Using Cacheset.exe from the Sysinternals Suite by MS solved the problem for me. Remember to run it as administrator, otherwise it will tell you that the values you entered are invalid.

Normally, caching the files should not be a problem, pushing other contents of the RAM out is. Check if you have the LargeSystemCache setting in HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management set. I suspect this is the real cause of the "clearing everything else" behavior. (My system was swapping out active processes while trying to cache a video I was encoding with avidemux).

I'm pretty sure what you're observing can't and shouldn't be disabled.

Every application can decide for itself to map a file into memory. And, to my understanding, that can drastically improve performance.

And, as you can see in your screenshot, the 4GB are already on Standby. Meaning they aren't actually any longer in use and can be re-assigned to new processes.