From 8.1 it seems possible to try the update from 8 to 8.1 and then to 10. Check this resource for more details on whether Microsoft can provide Windows 10 as a free upgrade to Windows 8.
From 8.1 it seems possible to try the update from 8 to 8.1 and then to 10. Check this resource for more details on whether Microsoft can provide Windows 10 as a free upgrade to Windows 8.