Getting the Windows Install Date from ALL of Your Computers

This script is inspired by a post I ran across on Windows Networking showing how to extract and format the Windows installation date via Powershell. This data would be useful to me for planning hardware refreshes.

On to the script!

################ BEGIN SCRIPT ################

#Purpose: To scan computers for Windows Install Date

#Choose whether this is an initial scan or a rescan
$InitialChoice = Read-Host "Enter 'I' for initial scan, or 'R' for rescan"

#Output file variables
$MissedComputersFile = "C:\Temp\Script - InstallDatesMissed.txt"
$OutputFile = "C:\Temp\Script - InstallDates.csv"

#Get the computer list, depending on initial choice
If ($InitialChoice -like "I"){
    $Computers = get-adcomputer -filter * | select name | sort name
} #End If

If ($InitialChoice -like "R"){
    $Computers = Get-Content $MissedComputersFile
    Remove-Item $MissedComputersFile -Force
} #End If

#Build an empty array for the data
$Results = @()

#Foreach computer in the list
Foreach ($Computer in $Computers){
    
    #Here I need to pick a naming method but it's dependent on where the data came from (the initial choice and subsequent computer name import)
    #For the initial scan, where data comes from AD:
    If ($InitialChoice -like "I"){$TestSystem = ($Computer.Name)}

    #For the rescan, where data comes from the text file:
    If ($InitialChoice -like "R"){$TestSystem = $Computer}
    
    #Test the connection
    If (Test-Connection -ComputerName $TestSystem -count 1 -quiet){
        
        #Create a new object to populate
        $ResultsEntry = New-Object System.Object
        
        #Get the computer's install date from WMI
        $InstallDate = (Get-WmiObject -ComputerName $TestSystem win32_operatingsystem | select @{Name="InstallDate"; Expression={$_.ConvertToDateTime($_.InstallDate)}}).InstallDate
        
        #Reformat the install date
        $InstallDateRefined = ($InstallDate.Year).ToString() + "-" + ($InstallDate.Month).ToString() + "-" + ($InstallDate.Day).ToString()
        
        #Add the name of the computer to the object
        $ResultsEntry | Add-Member -type NoteProperty -name Name -value $TestSystem
        
        #Add the install date to the object
        $ResultsEntry | Add-Member -type NoteProperty -name OSInstallDate -value $InstallDateRefined
        
        #Add the object to the array
        $Results += $ResultsEntry

        #Print a status message to the screen
        Write-Host -ForegroundColor Green "$TestSystem - Windows Install Date is $InstallDateRefined"
    } #End If
    
    #This runs if the test-connection is no good
    Else {
        
        #Adds the name of the system to the "Missed" file
        $TestSystem | Add-Content $MissedComputersFile

        #Print a status message to the screen
        Write-Host -ForegroundColor Red "$TestSystem - Not Online"
    } #End If
} #End Foreach

#Export the array to CSV
$Results | sort name | export-csv $OutputFile -NoTypeInformation

################ END SCRIPT ################

So after the initial script, you just feed it the "Missed" file over and over until you get everything.