As a few others have mentioned, it is the computer account itself not the user account.
ASP authentication errors like this are typically due to the computer account itself being passed as the authentication token instead of your user account.
If you are wanting Windows User account authentication for the ASP page instead try the following 2 options:
On the directory security tab in your IIS application directory, you need to set "Integrated Windows Authentication" to true so it knows to ask for your username and password.
Try adding this key to web.config:
<identity impersonate="true" UserName="YourDomain\=Your windows username" Password = "your windows password" />
More information about ASP impersonation settings can be found here: http://msdn.microsoft.com/en-us/library/aa292118%28VS.71%29.aspx