I don't recall a tweak.
It works for me, but on jpegs and other pictures, it seems to react slowly and intermittently......there are times when I can put the mouse on a pic and get no response for 5 seconds. I move the mouse to another pic and its size pops right up. I then go back to the first pic and it pops right up. Just not highly predictable for pictures. But I can't recall any other issues.
You might look at control panel/system/advanced system settings and play with the settings under "performance" area. I use custom settings in that location and have only 5 things checked, so I'm not sure there is anything there to help you.