IISLogFileCleanUp

Found the following script to delete old logfile

Option Explicit
Const GENERAL_FAILURE = 2
Const KillFile=0 ' Set this to 0 to not delete the files, set to 1 to delete the files

Dim ArgObj, Servername, WebSiteID, WebSite, WebSitepath, totalDeleted, MaxAgeOfFileToKeep


Function DeleteOldLogFiles(WebSite,  MaxAgeOfFile)
Dim File, ServerObj, FSO, FolderObj, FileObj, LogFileDir, Deleted, Status, FailedToDelete

Deleted = 0
FailedToDelete= 0

on error resume next

' Attempt to get the web site object from the metabase
Err.clear
Set ServerObj = GetObject(WebSite)
If (Err.Number <> 0) Then
   WScript.Echo "Error: " & Err.Description & " (" & Err.Number & ")"
   Exit Function
end if

LogFileDir = ServerObj.LogFileDirectory
Set ServerObj = Nothing

WScript.Echo "Log file dir for: " &WebSite & " = " & LogFileDir
WScript.Echo "Delete files over "& MaxAgeOfFile & " days old."
WScript.Echo ""
Set FSO = CreateObject("Scripting.FileSystemObject")
set Folderobj = FSO.GetFolder(LogFileDir)
for each File in Folderobj.files
  if (Date - File.DateCreated > cint(MaxAgeOfFile)) then
         Status = "Deleting File: " & File.name & ", Age=" & formatNumber(Date-File.DateCreated, 0)_
                       & " days, Status=" 
         Err.Clear
         if (KillFile = 1) then
             FSO.DeleteFile(LogFileDir & "\" & File.Name)
             If (Err.Number <> 0) Then
                    Status = Status & "Failed : "& Err.Description & " (" & Err.Number & ")"
                    FailedToDelete = FailedToDelete +1
            else       
                 Status = Status & "Deleted"
                Deleted = Deleted + 1
             end if
       else
            Status = Status & "Skipped"
        end if
        WScript.Echo Status  
  end if
next
DeleteoldLogfiles = Deleted

WScript.Echo ""
if (FailedToDelete > 0) then
   WScript.Echo "There were " & FailedToDelete  & " files that could not be deleted."
end if
WScript.Echo "There were " & Deleted & " files deleted."

end function

Sub DisplayHelpMessage()
    WScript.Echo
    WScript.Echo "Usage:"
    WScript.Echo "      DeleteOldWebSiteLogfiles.VBS MaxDays WebSiteNumber "
    WScript.Echo
    WScript.Echo "MaxDays = maximum age in days of files to keep."
    WScript.Echo "WebSiteNumber is the number of the web site, you have two methods to determine this:"
    WScript.Echo
    WScript.Echo "#1 = Run FINDWEB.VBS"
    WScript.Echo "#2 = Right click the web site, select properties, on the web site tab"
    WScript.Echo "     under logging click the Properties button, part of the log file"
    WScript.Echo "     name will contain the web site #"
    WScript.Echo
    WScript.Echo "     example log filename: W3SVC1\exyymmdd.log  - the web site is 1"
    WScript.Echo "                           W3SVC45\exyymmdd.log - the web site is 45"
-    WScript.Echo
    WScript.Echo "Please visit and support : http://www.iisfaq.com"
end sub

' Get the Arguments object
Set ArgObj = WScript.Arguments

' Test to make sure there is at least one command line arg - the command
If ArgObj.Count < 2 Then
        DisplayHelpMessage
        WScript.Quit (GENERAL_FAILURE)
End If

Servername = "LocalHost"
MaxAgeOfFileToKeep = trim(ArgObj(0))
WebSiteID    = trim(ArgObj(1))
WebSite        = "W3SVC/" & WebSiteID 
WebSitepath = "IIS://" & Servername &"/" & WebSite

TotalDeleted = DeleteOldLogFiles(WebSitePath,  MaxAgeOfFileToKeep)