Go start->run->type cmd hit enter. Type ipconfig /all.
On your PS3, go to your system setings, network settings,. Do a custom settings, do a manual for IP address change the last octet of your PC address to something that wouldn't be used (I use 64), subnet mask type what was on your PC, gateway type what was on your PC. Then continue, go onto DNS servers and change the DNS servers to what you saw on your PC, do the reast manual.
On your PC goto
http://portforward.com/routers.htm, select your router, select any program and it will tell you how to log in to your router. After you're logged in stop following the guide, look around for where it says DMZ, put you're PS3 in the DMZ and you'll be fine.