From Microsoft:
Windows 10 comes out on July 29th, but you might have to wait until
later to get it. Microsoft said today that it would be rolling out
Windows 10 in waves, "slowly scaling up" the rollout as it sees how
things are going. The intention seems to be playing it safe and making
sure that Windows 10 is getting a good response and running smoothly
across the millions of different systems out there. Microsoft may even
issue updates to Windows 10 between its July 29th release date and the
time that some early adopters are actually able to download it.
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Run CMD Prompt
Enter: wuauclt.exe/updatenow
Enjoy Windows 10