If you have about 25.9GB capacity on drive C: properties you still have the recovery partition and this will work for you. Windows update will work along with the store. If you have any questions, ask.
Download KB3173424 http://download.windowsupdate.com/d/msdownload/update/software/crup/2016/06/windows8.1-kb3173424-arm_e11b6837c0586d2b8d887f3bc33b3372fe83c8c7.msu
Download KB3172614 http://download.windowsupdate.com/c/msdownload/update/software/updt/2016/07/windows8.1-kb3172614-arm_3d918d6c809bf6f57c8fcefa5db5c739e1754426.msu
Download KB3097667 Windows RT 8.1 Update 3 Standalone Package https://www.microsoft.com/en-us/download/details.aspx?id=49143
You can put these on the SD card. All personal data on C: drive will be lost. Backup or move to SD card anything you want to save.
Reset your RT from within Windows. Reset, not refresh. Connect the RT to charge.
One of the pages will ask for a drive encryption key. Go to the bottom of the page and select ‘Not this Drive”
When the reset finishes, turn off WiFi, in settings go to ‘Power and Sleep’, ‘When plugged in’ set to ‘Never’
All updating is done from the Control Panel, Windows Update. Never use the troubleshooter to fix Windows Updates
After each search for updates is complete click on the blue line that says ‘important updates are available’ to see. You can speed things up by hiding all Office updates. Right click an Office update and select ‘Hide’.
Install all other updates found.
When Windows updates are all done and Update 3 is installed go back and restore hidden updates and install the Office Updates.
After installing each package of updates and the Windows Update page shows ‘Restart Now’, turn off WiFi and restart. After it restarts let the RT process the updates. When the disk usage finally goes down to zero you can go to the next step. To check disk usage, right clock the taskbar and select ‘task manager’, then the ‘performance’ tab.
Start Update Instillation Here
Turn on WiFi, Search for updates from the Control Panel, you will see a firmware update, install all Windows updates, restart
Search again for updates from the control panel
Again you will see a package of updates, this update should include Windows RT 8.1 Update 1 KB2919355, install updates, restart
Go to Windows Update. Check “installed updates” to see if KB2919355 is installed. KB2919355 has to be installed to proceed
Turn off Wifi
, install KB3173424, restart
Install KB3172614, restart
Turn on Wifi
, search for updates, should find over 200 updates, install, restart
Turn off Wi-Fi
and install KB3097667
After the restart, right-click on Taskbar > Properties, Start Menu. Check the box, Use the Start Menu instead of the Start Screen for no more metro screen.