I have Windows 8 Pro installed about 15 months ago.
Now I need to upgrade to Windows 8.1 Pro.
When I looked into the Store to update, it says 8.1 is 2.6GB.
Whereas in forums, I find the 8.1 pro ISO files about 1.4GB.
(I care for the size because I'm in India where our internet isn't that fast)
Can I download the 8.1 ISO file and install it using the existing Win8 key or do I need a new 8.1 key?