NT Authority/Network Service account has disappeared after reinstalling Sharepoint

Server O/S: Microsoft Small Business Server 2003 (Premium)
Software: IIS 6.0, ASP Net 2.0, Sharepoint Services 2.0, Sql Server 2000

Since having an IT consultant install the above on our new server, we have been having consistent issues with Sharepoint, which we found to be a result of the configuration database not being set correctly, which was conflicting with the Intranet Software we are running, Adenin IntelliEnterprise (which doesn't need Sharepoint to run, however would not run correctly, with Sharepoint having the configuration database errors).
As we were still having Sharepoint Errors after fixing the configuration database link (though not as many), our IT consultant recommended reinstalling Sharepoint. So I uninstalled, then reinstalled and configured as before. Everything works, except for some of the Intranet's applications which run on the Default Application Pool in IIS, which is assigned to the Network Service account. The applications are however looking for the account NT Authority/Network Services account, which has vanished from the server, and which appears to be set to an external domain. Because the software is configured to use the NT Authority/Network Service account it generates this error message in the log:
Event code: 3008
Event message: A configuration error has occurred.
Event time: 25/02/2007 12:26:12 PM
Event time (UTC): 25/02/2007 1:26:12 AM
Event ID: 882d58f397164877843b3ae6a9f829f3
Event sequence: 1
Event occurrence: 1
Event detail code: 0
 
Application information:
    Application domain: /LM/W3SVC/752176679/ROOT/adenin/GridViewer-1-128168403636516833
    Trust level: WSS_Minimal
    Application Virtual Path: /adenin/GridViewer
    Application Path: C:\Program Files\adenin\GridViewer\
    Machine name: BWESLIVE
 
Process information:
    Process ID: 1296
    Process name: w3wp.exe
    Account name: NT AUTHORITY\NETWORK SERVICE
 
Exception information:
    Exception type: HttpException
    Exception message: Could not load file or assembly 'ActiveReports.TiffExport, Version=3.3.1.2009, Culture=neutral, PublicKeyToken=cc4967777c49a3ff' or one of its dependencies. Failed to grant minimum permission requests. (Exception from HRESULT: 0x80131417)
 
Request information:
    Request URL: http://localhost/adenin/GridViewer/GridViewer.aspx?gid=1&height=500&tr=1000024&vid=1000067&clickurl=portal.asp?b6sid=5weKgSS4UIhEDoPbG3Mrd&bo=b6dm3.b6udm&tr=1000024&viewid=1000067&viewmode=id&tbAction=view
    Request path: /adenin/GridViewer/GridViewer.aspx
    User host address: 127.0.0.1
    User:  
    Is authenticated: False
    Authentication Type:  
    Thread account name: NT AUTHORITY\NETWORK SERVICE
 
Thread information:
    Thread ID: 1
    Thread account name: NT AUTHORITY\NETWORK SERVICE
    Is impersonating: False
    Stack trace:    at System.Web.Compilation.BuildManager.ReportTopLevelCompilationException()
   at System.Web.Compilation.BuildManager.EnsureTopLevelFilesCompiled()
   at System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters)
 
The following DCOM error message is also referencing this account:

The application-specific permission settings do not grant Local Activation permission for the COM Server application with CLSID
{0C0A3666-30C9-11D0-8F20-00805F2CD064}
 to the user NT AUTHORITY\NETWORK SERVICE SID (S-1-5-20).  This security permission can be modified using the Component Services administrative tool.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.

If I could find the NT Authority/Network Service account, I could fix this issue, however whereas before I could set folder securities to allow this account levels of control, when I try to do this now, it cannot find the object NT Authority/Network Service account, and in Active Directory Users, I can only find references to this account, inside other user groups which include it, however these references all say that the user is a placeholder from an external domain.

I can provide a word document with screenshots if anyone wishes.

NT Authority/Network Services existed prior to reinstalling Sharepoint.

My server is the domain controller, and I am logging in as the administrator Start Free Trial