System.UnauthorizedAccessException: Access is denied

[Efi]

Hi,
We have a simple 3 tier application which its core application is VC++ 6.0
ATL COM running as a server application in the COM+. An asp pipe is in charge
of handling the requests and passes it to the COM for processing.

We are now trying to migrate the asp pipe to Asp.Net.

When running the above configuration with Asp.Net on IIS 5.0 (W2K) we have
no problems but when trying the do it on IIS 6.0 (W2K3) we are getting the
following error which is basically access denied error on the line that tries
to create the COM instancing.
Access is denied.
Description: An unhandled exception occurred during the execution of the
current web request. Please review the stack trace for more information about
the error and where it originated in the code.

Exception Details: System.UnauthorizedAccessException: Access is denied.

ASP.NET is not authorized to access the requested resource. Consider
granting access rights to the resource to the ASP.NET request identity.
ASP.NET has a base process identity (typically {MACHINE}\ASPNET on IIS 5 or
Network Service on IIS 6) that is used if the application is not
impersonating. If the application is impersonating via <identity
impersonate="true"/>, the identity will be the anonymous user (typically
IUSR_MACHINENAME) or the authenticated request user.

To grant ASP.NET write access to a file, right-click the file in Explorer,
choose "Properties" and select the Security tab. Click "Add" to add the
appropriate user or group. Highlight the ASP.NET account, and check the boxes
for the desired access.

Source Error:
An unhandled exception was generated during the execution of the current web
request. Information regarding the origin and location of the exception can
be identified using the exception stack trace below.

Stack Trace:

[UnauthorizedAccessException: Access is denied.]
BurstingPipe.Net.WebForm1.Page_Load(Object sender, EventArgs e) in
d:\burstingweb\burstingpipe.net\adserverpipe.aspx. cs:160
System.Web.UI.Control.OnLoad(EventArgs e) +67
System.Web.UI.Control.LoadRecursive() +35
System.Web.UI.Page.ProcessRequestMain() +731

I've tried to set permissions (ASPNET and Network Service) on files and in
the COM+ (Launching permissions).

Help Please!!!

Thanks,

Efi