(Note: This is relevant only for XP and prior, which our lab still has.)

If we test for "HKLM\SOFTWARE\Classes\IMECheckDefaultInputProfile.Japan" (using Japanese as an example), we can tell if the East Asian Language pack is installed.

$reg = [Microsoft.Win32.RegistryKey]::OpenRemoteBaseKey('LocalMachine', $myComputer);
$subKey= "SOFTWARE\Classes\IMECheckDefaultInputProfile.Japan" -replace '\\', '\\';
if (!($reg.OpenSubKey($subkey))) { $pass = $false; }