OS is Operating System.
Do you use Windows 7, 8, 10? Or Linux (doubt Linux since you gotta know stuff about PC's to even do anything, XD)
What program are you running to draw in? Photoshop, Krita, Gimp, Paint ToolSAI, etc?
I would recommend Movie Maker 12 with the Windows Live bundle pack, but you can choose what to install. It gives a lot of options. More optimized for sure, and you can custom nearly everyaspect of saving... to the one drawback of only 16x9 or 4x3. I like doing KH2FM stuff in 21x9 but have to save vids with annoying back bars.