Ok let's see...
I checked to see if your modem/router has a Nat firewall built in and it has, so here are your instructions to Port Forward, it's not to technical just follow each step and don't forget to set up the Static IP part as it is very important, that also has a step by step guide for Vista, just click on the link provided in the details...
Let me know how you get on...
Port Forwarding for the INEXQ BR400