In Linux, we are used to mount the hard disk and then look at /etc/issue, /etc/redhat-release or something similar. You can even see the kernel version in the file names of the installed kernel images in /boot.
But for a Windows OS? Well, you could look at the version of ntoskrnl.exe, for instance.
Here are the version numbers for different versions of Windows :
wine sigcheck -q -n ntoskrnl.exe
File Version : 6.1.7601.23677 (win7sp1_ldr.170209-0600)