PowerShell function to compute a MD5 checksum for a file. Based on an answer at http://stackoverflow.com/questions/10521061/how-to-get-an-md5-checksum-in-powershell. Note, this method works for files greater than 2GB in size.

Get-MD5Hash

function md5hash($path)
{
    $fullPath = Resolve-Path $path
    $md5 = new-object -TypeName System.Security.Cryptography.MD5CryptoServiceProvider
    $file = [System.IO.File]::Open($fullPath,[System.IO.Filemode]::Open, [System.IO.FileAccess]::Read)
    [System.BitConverter]::ToString($md5.ComputeHash($file))
    $file.Dispose()
}