Windows 10 is finally here, almost a year after it was first announced. Microsoft officially released its new operating system on Wednesday in 190 countries.

If you haven’t been following along, Windows 10 is the most secure version of the operating system yet, and includes plenty of new features, some of which were carried over from Windows 8. Users will note the return of the Start menu, a slick new browser called Microsoft Edge, and support from Microsoft’s digital assistant Cortana on the desktop. There’s also Continuum, which automatically adjusts from touch controls to a mouse and keyboard setup when you switch from tablet to laptop mode on a hybrid device.

Microsoft says millions of reservations have already been booked, and it’s rolling out the release in phases. It may not be available immediately, but if you have a “genuine” Windows 7 or Windows 8.1 PC or tablet, you’ll eventually get Windows 10 for free. When the upgrade is ready, you’ll see a notification in the taskbar letting you know.

New devices with Windows 10 pre-installed are also available for purchase from Lenovo, HP, Dell and Acer today. Additional hardware is set to launch in the next few weeks, including some products that are designed to work specifically with Microsoft’s new Windows Hello biometric software.

Microsoft says it plans to flood the market with Windows 10 products in time for the holidays, but for now just keep an eye out for that update on your current Windows machine.