Microsoft Windows Operating System & version can be determined following below steps;
Click Run or if you see “Start Search” field click in it or just type winver and press Enter.
This will pull up a new About Windows window giving you the version of Microsoft Windows, the build info, and service pack information if any service pack is installed as shown below.
Right-click on My Computer.
Click on Properties. In the System Properties window the Service Pack (if installed), along with operating system & version will be seen.