The upcoming OS update will require a lot of free space on your tablet
As part of the Windows 8.1 update cycle, Microsoft will also roll out improvements for the Windows RT platform that’s currently installed on a number of devices, including its own Surface RT tablet.According to some leaked system requirements that reached the web during the weekend, Windows RT 8.1 Preview requires a PC already running Windows RT with 10 GB of free storage space.
While 10 GB is clearly a lot of space for an OS update, it could be a problem for Surface RT owners who purchased the 32 GB model.
As you probably know, the 32 GB version of the Surface RT has approximately 15 GB free hard disk space, which means that your installed apps, settings, and files should eat up a maximum of 5 GB on your disk in order to install the 8.1 Preview.
System requirements for desktop computers and laptops are available here.