Latitude E5450 Windows 10 Graphic Problems

I have a Latitude E5450 with a dedicated Geforce 840M. Laptop came with Windows 10 preinstalled but all Windows animations (such as Start Menu for instance) are extremely slow. I also tried running a few benchmarks/game (such as DotA 2) and performance are terrible. It seems like the system is using the integraded Intel HD card instead of the 840M. I tried installing Windows 7 and performance are perfect so it must be a driver issue.

Many thanks.