The FreeSpace property contains the amount of free space available.
<html> <script language="JScript"> <!-- var drivePath = "C:"; var fileSysObj = new ActiveXObject("Scripting.FileSystemObject"); var drive = fileSysObj.GetDrive(fileSysObj.GetDriveName(drivePath)); document.write("Drive ",drivePath," has ",drive.FreeSpace," free space."); --> </script> </html>