I have been having problems with my computer not showing the windows contents while dragging. About once every 2 weeks, I will turn on my computer and that function will be disabled. So what I would do is go to Computer Properties -> Advanced System Settings -> Performance Settings, and then check the "Show window contents while dragging checkbox.
Today however, in the last 2 hours, the function has just disabled itself 3 times already. Everytime, I go through the same process to turn it on and it just won't stick for more than an hour.