First off, the Linksys BEFSX41 is a great router. My favorite feature of this router is the Stateful Packet Inspection (SPI).
Forwarding ports with this router is quite easy.
First of all, goto http://192.168.1.1
The default password is 'admin'
Click the 'Advanced' Tab on the top right
Click the 'Forwarding' Tab
Enter in the extension port range, check TCP and/or UDP and specify the Internal LAN IP address of the computer you want to forward the port to. Click 'Enable" and then 'Apply'
Hopefully, this will have forwarded the port to the correct machine.
On a side note, It is recommended that you use static ip address for computers with forwarded ports.
