Windows 7, 8 and 8.1 users can now reserve their free copy of Windows 10
Just yesterday, the pricing for Windows 10 version was leaked and today it seems that Microsoft is starting some pre-enrollment for Windows 10. Multiple users on twitter are reporting that they are receiving a taskbar bubble which asks them to reserve their version of Windows 10.
Microsoft already confirms that they'll be coming out to give free Windows 10 upgrades for all Windows 7 and Windows 8.1 users within the first year. Since announcing that, there was no official timeline as to when users will be able to take advantage of this offer until today.
The bubble popping up on taskbars is indeed the road to Windows 10. From the opened windows, users will be given the choice to reserve their free Windows 10 upgrade today and this is probably there to reduce the server stress when Microsoft actually releases it to the public later this year. A 3GB download is required when updating to Windows 10.