Remote desktop port forwarding

Hi,

I am running Windows XP SP3 on my desktop machine (mic-desktop) inside
my home LAN.
I have remote desktop turned on and am able to use it properly from
another computer in my network.

What I'd like to do is be able to remote desktop mic-desktop from
outside the network.
I have configured my router to forward port 3389 to mic-desktop.
However, this doesn't seem to do the job properly. I have forwarded
other ports, so the problems is not within the router. Also, the
Windows Firewall is configured properly.

I'm guessing there's some extra configuration needed because I'm using
SP3.
Any help is appreciated.

Michel