Firstly, make sure you install the virtualbox guest tools. This will surely speed up the virtualization. Also, try increasing the amount of memory you give the VM. Although I'm assuming you don't have much memory to work with as I'm guessing your Atom N455 is in a Netbook, probably with 1 GB of RAM. Also, which version of windows are you running. You might want to try with Windows XP or even earlier (although I don't think anything earlier will run Netflix). Also, try adjusting the video quality on your movies, you can make it play in SD if you want. Lastly, you may just not have enough power to do this. Running in a VM is pretty slow. It's not really designed to do multimedia things like video and games. Most applications work alright, but anything with lots of moving stuff on the screen tends to be pretty slow.