You are comparing a laptop graphics card with a desktop graphics card… not to mention that the 5xx series was a beast at rendering…
Moreover, rendering via viewport brings in a whole host of other potential issues… can you do test renders via commandline and see what the speed difference is there?
Two things that would differ… static BVH vs dynamic BVH (actual rendering always uses static BVH over dynamic) and tile sizes… From Memory, the tile size for viewport is 100%… where as the tile sizes for rendering is that that is set… Try increasing the tile size.
GTX 570 is a considerably better GPU, so no surprises there.
Progressive render in the viewport works differently than a full render - that’s why
you can use tile sizes to your advantage only when doing the latter. It obviously doesn’t render
in tiles in the viewport.
Win 8(.1) is the best Microsoft OS so far, you just have to know how to use it.
Right click on the battery icon near the clock and select Power Options and then change plan settings.