Well a little more info would be helpful in giving you some suggestions CirroFox.

1.  Are both systems connected to each other via a switch only (ie. in the same room on a real physical LAN not a virtual LAN ala Hamachi etc.) ?

2.  Wired or WiFi?

3.  What type of security software on each of the machines if any?

4.  Firewalls?

Without answers to those questions you're most likey not going to get any further.....

Here's the thing.

If you just want to play a game between the both of you (without other people) then just do the following:

1.  Find out the IP address of the system you want to connect to (START >> RUN >> IPCONFIG)

2.  Click "Multiplayer" in SINS instead of IronClad Online and then "Join IP" (using the IP you just found)

If you do want to play with others online you'll have to deal with the fact that both of you want to go out and then back in (to/from the internet) over the same router.

1.  You'll need to modify one of the games hosting ports in the user.setting file

2.  Then you'll need to forward the default hosting port from the router to the machine you left unchanged, and forward the new port to the machine on which you changed it in the user.setting file.

I wrote a guide a few years ago with the steps needed for router config etc. which you can find in a sticky in the "technical" section of the sins forums if you need help with router config.

thanks,

the Monk