I build a COM+ and installed in a Windows 2003 server as an application with the DCOMCNFG tools. Create the MSI client installation proxy and install the client in my xp machine.
W2K3 server is not part of the domain and in a different network protected by a firewall.
The COM+ application is running under the administrator Account (impersonation) but the problem is that I'm getting access denied message all the time.
I'm able to ping and browse to the W2k3 server without problem. (Username/password is prompted when try to browse the W2k3 server disk. Thast because is in a different network as my machine.)

Client -> 172.16.x.x network (ABC Domain)
W2k3 Server -> 10.10.x.x network (Not part of ABC Domain)