Remember the size of the drive where your Windows is installed? If you haven’t been downloading large files over the last few hours and the size has shrunk a bit then there is only one reason why that is the case.
Windows 10 is coming. Tomorrow. Just in case you didn’t know. Microsoft already promised a smooth upgrade process and even has an elaborate process to get everyone on Windows 7 Service Pack 1 and Windows 8.1 to reserve their upgrade slot so that they are notified when time to upgrade comes. Thanks to this, Microsoft appears to be already seeding the update files to several eligible users with compatible machines in preparation for the big upgrade in coming days.
For those whose Windows 10 installation files have already finished downloading, it’ll be unlocked and activated at exactly midnight when it is officially July 29th and users will start being notified to make the jump to Windows 10.
Check C:\$Windows.~BT on your machine to see if there are some updated files.