Many System Info tools, including a few that come with Windows, can easily tell you what version and build of Windows Operating System you are running but none of them reveals when the system was installed. But if you are interested in this piece of information, here is an easy way to find out.
On Windows 10 and 8.1 computers
Open up PowerShell window and type the following cmdlet.
GCIM Win32_OperatingSystem | Select Caption, Version, InstallDate, OSArchitecture, LastBootUpTime
Note that on Windows 10 the InstallDate shows the date when last build of Windows 10 was installed. I installed Windows 10 on this computer a few months ago but the latest build which is 10547 was installed on Sept. 21, 2015.
Since Windows 8 doesn’t have the same upgrade as Windows 10, the InstallDate you get on Windows 8 computers is the actual date it was installed.
ON Windows 7 computers
GCIM isn’t recognizable on Windows 7 because of the version of PowerShell. So try the following cmdlet instead, which is slightly different.
Get-WmiObject -Class Win32_OperatingSystem | Select Caption, Version, InstallDate, OSArchitecture, LastBootUpTime
As you can see, the information both cmdlet collected are the same. It’s just that GCIM displays the result especially the date format a lot nicer.
Also note that I threw in the “LastBootUpTime” parameter in the command so it will reveal when the system was booted up last time. Just another piece of useful information to have in handy.