I'm sorry about how simple the question is but I've searched all over the Internet and I found MSDN articles about making application pools (http://msdn.microsoft.com/en-us/library/ms525309.aspx) and using IIS 7 but nothing about IIS 6 and applications.
I'm currently using the following code to create an application and set its properties:
Set oWebAdmin = GetObject("winmgmts:root\WebAdministration")
' Define the Path, SiteName, and PhysicalPath for the new application.
strApplicationPath = "/B2"
strSiteName = "Default Web Site"
strPhysicalPath = "C:\inetpub\wwwroot"
' Create the new application
oWebAdmin.Get("Application").Create "/B2", "Default Web Site", "C:\Inetpub\wwwroot\B2"
Set app = oWebAdmin.Get("Application.SiteName='Default Web Site',Path='/B2'")
app.AuthFlags = 21
app.NTAuthentication="yourfriendlydomain.helloworld.com"
However, I get 0x8004100E (Namespace specified cannot be found.) and I haven't got the faintest idea how to proceed.
root\WebAdministration is new to IIS 7. Since you're using IIS 6, adsutil.vbs is the way to go, or else script it directly with ADSI.
I don't have a script to include as an example but I googled and found this: http://blogs.msdn.com/david.wang/archive/2007/12/12/howto-create-custom-application-pool-by-commandline.aspx