first, assign an IP address to your PC (ahh, this is so hard to explain. But nevermind, I'll explain to you)
Windows Vista / 7
1. Open the Network and Sharing Center.
2. Locate your Connection, (it should be the Local Area Connection (or Network)).
3. Click View Status
4. Click Properties
5. TCP/IP V4 : properties
6. set to Assign Manually
7. Enter an IP address, simillar to your router's addres. (If router: 192.168.1.x, then IP = 192.168.1.x. If 192.168.0.x, then put 192.168.0.x too)
8. Subnet mask: just use 255.255.255.0
9. Default Gateway: your router's IP
10. click OK.
The internet will be reset for some seconds. if you lost your internet connection, change them to be assigned automatically and tell me what happened.
then, on port forwarding:
Forward every port to your PC's IP address.
*You can find this similar guide I wrote in rAthena. but sorry, I forgot where did I put the complete guide.