Here's a simple script to get disk space and size.
Written this in 2 mins, a personal record
Code:

Function DiskSpace
  Dim $WshShell, $fso, $Drive, $DriveCol, $drv
  $WshShell = CreateObject("WScript.Shell")
  $fso = CreateObject("Scripting.FileSystemObject")
  $DriveCol = $fso.Drives
  For Each $Drive in $DriveCol
    If $Drive.DriveType = 2
      $drv = $fso.GetDrive($Drive)
      ? "Free Space of " + $Drive " = " + $drv.FreeSpace / 1024 / 1024 / 1024 + " GB"
      ? "Total Space of " + $Drive " = " + $drv.TotalSize / 1024 / 1024 / 1024 + " GB"
    EndIf
  Next
EndFunction