The application runs as Windows Service which is hosted by the Windows
Service Controller, which is very different from other applications (you know, it allow the service running when the user logs out on logs on, without the desktop, and so on).
Even though you can configure different services to run under different user accounts, including "usual" user account, it does not normally run under any of such accounts. Also, you should understand the "Administrator" account is not essentially different from other user accounts; it's just set up by the OS installation first, assigned to "Administrators" group and some predefined sets of privileges are assigned to this group and member. Later on, you can create more accounts with exact same privileges and even remove "Administrator". The bottom line is: for most or all services, including IIS, such accounts are totally unsuitable. They are used to work on a desktop, in contrast to the Services.
So, the Services are usually run under special accounts like "Local System", "Local Service" or "Network Service".
You can see what account is used by IIS: show the "Administrative Tools" applet "Services". (By the way, you can start it from command line as
%windir%\system32\services.msc
.) You will find IIS service process running under the name like "World Wide Web Publishing Service".
See the privileges of the NetworkService account:
http://msdn.microsoft.com/en-us/library/windows/desktop/ms684272%28v=vs.85%29.aspx[
^].
This is just to answer your exact question (the answer is: none of them) and help to understand the service hosting and accounts.
I'm afraid you provided not enough information to actually fix the problem. To do this, you should study the runtime of your application and find out where the exception is thrown. Detailed logging can help.
—SA