From http://www.w3schools.com (Copyright Refsnes Data)

ASP FreeSpace Property

The FreeSpace property returns the amount of free space to a user on the specified drive or network share.

Note: The value returned is often equal to the value returned by the AvailableSpace property.

Syntax

DriveObject.FreeSpace

Example

<%
dim fs,d
set fs=Server.CreateObject("Scripting.FileSystemObject")
set d=fs.GetDrive("c:")
Response.Write("Drive " & d)
Response.Write(" Free space in bytes: " & d.FreeSpace)
set d=nothing
set fs=nothing
%>

Output:

Drive c: Free space in bytes: 884465664

Complete Drive Object Reference