Windows 10 is almost here. It will be available free from July 29, 2015. The conditions for the free upgrade are:
"Yes, free! This upgrade offer is for a full version of Windows 10, not a trial. 3GB download required; standard data rates apply. To take advantage of this free offer, you must upgrade to Windows 10 within one year of availability. Once you upgrade, you have Windows 10 for free on that device.
Windows 10 Upgrade Offer is valid for qualified Windows 7 and Windows 8.1 devices, including devices you already own. Some hardware/software requirements apply and feature availability may vary by device and market. The availability of Windows 10 upgrade for Windows Phone 8.1 devices may vary by OEM, mobile operator or carrier. Devices must be connected to the internet and have Windows Update enabled. Windows 7 SP1 and Windows 8.1 Update required. Some editions are excluded: Windows 7 Enterprise, Windows 8/8.1 Enterprise, and Windows RT/RT 8.1. Active Software Assurance customers in volume licensing have the benefit to upgrade to Windows 10 enterprise offerings outside of this offer. To check for compatibility and other important installation information, visit your device manufacturer’s website and the Windows 10 Specifications page. Additional requirements may apply over time for updates. Security and features are kept automatically up-to-date which is always enabled. See the Windows 10 How to Upgrade page for details. "