ASPNET

I was playing around with some code that we use in one of my Microsoft courses.  Not a complex example, and it assumes you've granted privledges to the ASPNET account datareader for Northwind.  No biggie I guess (this is actually quite common in courses that don't focus on ASP.NET.  Getting into identity might be considered overkill for many of these classes).  Well, this is all fine and dandy unless you are running 2003.  I get a big ol' Login failed for user 'NT AUTHORITY\NETWORK SERVICE' error message thrown at me.  Bastards! 

I have a feeling that I'm going to have to spend a lot more time figuring this stuff out than I did with IIS 5.0.  Anyone have any good links?