object.DriveLetter 

function ShowDriveLetter(drvPath)
{
   var fso, d, s;
   fso = new ActiveXObject("Scripting.FileSystemObject");
   d = fso.GetDrive(fso.GetDriveName(drvPath));
   s = "Drive " + d.DriveLetter.toUpperCase( ) + ": - ";
   s += d.VolumeName + "<br>";
   s += "Available Space: " + d.AvailableSpace/1024 + " Kbytes";
   return(s);
}

Function ShowDriveLetter(drvPath)
   Dim fso, d, s
   Set fso = CreateObject("Scripting.FileSystemObject")
   Set d = fso.GetDrive(fso.GetDriveName(drvPath))
   s = "Drive " & d.DriveLetter & ": - " 
   s = s & d.VolumeName & "<BR>"
   s = s & "Free Space: " & FormatNumber(d.FreeSpace/1024, 0) 
   s = s & " Kbytes"
   ShowDriveLetter = s
End Function