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Anyone know how can open some application running in my windows 2003 server guest in to my windows XP host, I try to reach some webapplication in my windows 2003 server guest.

You're not very clear on what you want to accomplish. If you want to access a website that's hosted on the Guest, then all you need to do is configure the Guest networking settings to Host-Only or bridged. The latter is preferred as it will allow the Guest to be like a normal machine on the network, but sometimes it doesn't work properly between Host and Guest. Host-Only is then the thing you need to use, but you will need a second NIC for internet in the VM.
One last thing you can use is NAT and forward some ports, as described in the manual.

Thanks, I tried with the port Forwarding in NAT mode, but It doesn´t work, It´s mean from Host can´t reach the web app in the guest.
I´ll try with the host mode only and the second NIC in the VM, It´s any special config to do this?

When you used NAT, how did you connect? You did use the Host IP address (or localhost) to get to the Guest on the forwarded port right? So if you forwarded port 8080 to 80 in the Guest, you use localhost:8080 to get to the Guest webserver.
For Host-Only, you have to make sure that you configured it in the VB settings. This is not done in the VM settings itself, you only select the attached NIC there.