getfileassoc.ps1

$associations = @()
$registryPaths = @(
    "HKLM:\Software\Classes",
    "HKCU:\Software\Classes"
)

foreach ($path in $registryPaths) {
    Get-ChildItem $path | ForEach-Object {
        if ($_.PSChildName -like ".*") {
            $extension = $_.PSChildName
            $progId = (Get-ItemProperty -Path "$($_.PSPath)" -ErrorAction SilentlyContinue).'(Default)'
            
            if ($progId) {
                $commandPath = (Get-ItemProperty -Path "$path\$progId\shell\open\command" -ErrorAction SilentlyContinue).'(Default)'
                
                $associations += [PSCustomObject]@{
                    Extension       = $extension
                    ProgID          = $progId
                    AssociatedApp   = $commandPath
                }
            }
        }
    }
}

$associations | Out-GridView -Title "File Extensions and Associated Applications"