Microsoft reveals how much of Surface RT's disc space is actually yours
 

If you've wondered how much space Windows RT, Office and Microsoft's bundled apps occupy on your shiny new Surface RT, worry no longer. Microsoft has revealed that once you've accounted for binary conversion, recovery provision and the software itself, the 32GB device will have 16GB of free space, while 64GB units will get 46GB of room to store your media. Naturally, you can use microSD cards (or USB Drives) to add to that space, and if you'd like to know how to get the device to treat it as if it's all coming from a single library, check out our tutorial.

http://www.engadget.com/2012/11/05/s...orage-figures/