if (-not (dir cert:\currentuser\My | Where-Object {$_.Thumbprint -eq "5649d14b2abbafa50123456"})) {
$cert = New-Object System.Security.Cryptography.X509Certificates.X509Certificate2
$cert.Import("c:\certs\Certificate.pfx","PlainTextPassword",[System.Security.Cryptography.X509Certificates.X509KeyStorageFlags]"UserKeySet")
$store = New-Object System.Security.Cryptography.X509Certificates.X509Store "My", "CurrentUser"
$store.Open("ReadWrite")
$store.Add($cert)
$store.Close()
}
The original script has been copied from:
http://social.technet.microsoft.com/Forums/windowsserver/en-US/28bd6ad1-0627-420c-b995-1ab420710b54/automating-ca-certificate-installtion?forum=winserversecurity