Determining the logged-on user from ASP

If you're using Basic or NT Challenge/Response security for access to 
your Web site, you can programmatically determine which user is 
accessing a page at any given time. To do so, simply interrogate the 
value of the following:

request.serverVariables("LOGON_USER")

Note that, by definition, you'll simply get back an empty string if 
you're using anonymous security on your Web site.