Windows Server versions and lifecycle

You’ll check versions the way admins do on real servers: from the operating system itself, and from the install media before anything is installed. Steps 2 to 4 need an administrator PowerShell window: right-click Windows PowerShell and choose Run as administrator.

1Check your own Windows version two ways

In a normal PowerShell window, run these one at a time:

Get-CimInstance Win32_OperatingSystem | Select-Object Caption, BuildNumber
Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion' | Select-Object ProductName, DisplayVersion, CurrentBuild, UBR

On Windows 11 you should see something like this:

Caption                  BuildNumber
-------                  -----------
Microsoft Windows 11 Pro 26100


ProductName    : Windows 10 Pro
DisplayVersion : 24H2
CurrentBuild   : 26100
UBR            : 6899

Look closely: the registry says Windows 10 Pro on a Windows 11 laptop. The ProductName value was never updated when Windows 11 came out.

The build number, 26100, is the reliable part. UBR (update build revision) is the number after the dot, and it goes up every Patch Tuesday, so build 26100.6899 tells you exactly which monthly update is installed.

✅ Checkpoint: You have your build number and UBR, and you’ve seen why the build is more trustworthy than a product name.

2Open the Server 2025 ISO without installing it

In an administrator PowerShell window, run this:

$iso = Mount-DiskImage -ImagePath C:\Lab\ISO\server2025.iso -PassThru
$drive = ($iso | Get-Volume).DriveLetter
"ISO mounted as drive $($drive):"

You should see something like this:

ISO mounted as drive E:

Mount-DiskImage attaches the ISO as a virtual DVD drive, exactly like double-clicking it in File Explorer. Your letter may be D:, E: or F:.

✅ Checkpoint: PowerShell printed a drive letter, and that drive shows up in File Explorer.

3List the editions inside the ISO

Run this:

Get-WindowsImage -ImagePath "$($drive):\sources\install.wim" | Select-Object ImageIndex, ImageName

You should see something like this:

ImageIndex ImageName
---------- ---------
         1 Windows Server 2025 Standard Evaluation
         2 Windows Server 2025 Standard Evaluation (Desktop Experience)
         3 Windows Server 2025 Datacenter Evaluation
         4 Windows Server 2025 Datacenter Evaluation (Desktop Experience)

One ISO, four choices. The names without “(Desktop Experience)” are Server Core.

install.wim is the file Windows Setup copies onto the disk, and each image inside it is one edition and install type. In Lesson 5 you’ll choose index 4 for DC01.

✅ Checkpoint: You can see four images: Standard and Datacenter, each as Server Core and as Desktop Experience.

4Look inside one image, then close the ISO

Run this:

Get-WindowsImage -ImagePath "$($drive):\sources\install.wim" -Index 4 | Select-Object ImageName, Version, Languages, @{n='SizeGB';e={[math]::Round($_.ImageSize/1GB,1)}}
Dismount-DiskImage -ImagePath C:\Lab\ISO\server2025.iso | Out-Null

You should see something like this:

ImageName : Windows Server 2025 Datacenter Evaluation (Desktop Experience)
Version   : 10.0.26100.1742
Languages : {en-US}
SizeGB    : 9.6

Version shows the build and the update level the ISO was made with. A fresh install starts at that level, and Windows Update brings it up to date afterwards. Out-Null hides the dismount output you don’t need.

✅ Checkpoint: You can see the build number of your ISO, and the drive letter has disappeared from File Explorer.

5Count the days each version has left

Paste this whole block into a normal PowerShell window:

$versions = @(
    [pscustomobject]@{ Version = 'Windows Server 2012 R2'; Build = 9600;  UpdatesUntil = [datetime]'2026-10-13' }
    [pscustomobject]@{ Version = 'Windows Server 2016';    Build = 14393; UpdatesUntil = [datetime]'2027-01-12' }
    [pscustomobject]@{ Version = 'Windows Server 2019';    Build = 17763; UpdatesUntil = [datetime]'2029-01-09' }
    [pscustomobject]@{ Version = 'Windows Server 2022';    Build = 20348; UpdatesUntil = [datetime]'2031-10-14' }
    [pscustomobject]@{ Version = 'Windows Server 2025';    Build = 26100; UpdatesUntil = [datetime]'2034-11-14' }
)
$versions | Select-Object Version, Build, @{n='DaysLeft';e={($_.UpdatesUntil - (Get-Date)).Days}}

On 19 October 2026 you would see this (your numbers depend on today’s date):

Version                Build DaysLeft
-------                ----- --------
Windows Server 2012 R2  9600       -6
Windows Server 2016    14393       84
Windows Server 2019    17763      812
Windows Server 2022    20348     1820
Windows Server 2025    26100     2947

A negative number means the date has passed: a 2012 R2 server gets no more security fixes at all. Subtracting two dates gives a time span, and .Days takes the whole days from it. This is the start of a real lifecycle report; in Phase 2 you’ll feed it a list of servers instead of typing the versions in.

✅ Checkpoint: Your table shows a negative number for 2012 R2 and the most days for 2025.