All we have to do is write a WMI query that includes the path of the folder we want to check as well as the file extension we’re checking for. For example, this script retrieves a collection of all the .bak files found in the C:\Logs folder:

Option Explicit

Dim wmiService, files

Set wmiService = GetObject( "winmgmts:\\.\root\cimv2" )

Set files = wmiService.ExecQuery( _

    "SELECT * FROM CIM_DataFile WHERE Path = '\\Logs\\’ " & _

    "AND Drive = 'C:’ AND Extension = 'bak’" )

Print "Number of .bak files found: " & files.Count

If you look closely at this script you might notice a couple things. First, we didn’t specify the path as C:\Logs; instead, we separated the drive (C:) from the folder (Logs). Why did we do that? Well, because – for better or worse – that’s how the CIM_DataFile class works; what we think of as the file path is divided up between the drive and the folders. The Drive parameter is actually optional here; we could leave it out unless we also have a folder named D:\Logs. If that was the case, then the Drive parameter becomes mandatory; leave it out, and the query returns all the files found in a folder with the path Logs. That would include D:\Logs (and E:\Logs and F:\Logs and …) as well as C:\Logs.

Second, you might note that we used double \\’s to surround the Path; thus we have \\Logs\\ rather than \Logs\ (i.e., C:\Logs ). Why? Again, that’s just the way WMI works; any time you include a file path in a WHERE clause you need to use two \\’s.

Based on "How Can I Tell if a Folder Has Any Files with a Specific File Extension?" from the Scripting Guys.