Windows users often find themselves frustrated with the frequency and timing of update prompts that can appear unexpectedly. Complaints about these updates usually revolve around two major points: their overwhelming number and the fact that they often require a system restart at inconvenient...
Microsoft recently made the Windows 10 upgrade a recommended one meaning if your settings in Windows updates is set to automatically install then you will automatically upgrade to Windows 10.
Here's a few tips from Winbeta.com on how to avoid an unwanted upgrade:
Reference
automatic install
control panel
pc settings
recommended update
security updates
settings
software management
system maintenance
tech support
update control
update notifications
updatetips
upgrade
upgrade process
user guide
windows 10
windows 7
windows 8.1
windows update