ICS and File Sharing port problem

[Dudlington]

OK, i recently set up some spare computer parts out of an old record player to use to share an internet connection and some files. My DSL line is hooked up to it, then shared over a bridged connection (WinXP on all machines) to my main PC and my neighbours by 2 network cards (I'm too cheap to get a router).

The problem is that I have noticed DC++/Direct Connect will only work in Passive Mode (for people behind a firewall) and quite a few IRC FServs don't seem to work anymore. It would seem as if some ports are being blocked, but I have always run my main machine without a firewall, where these things worked fine, and I made sure that the WinXP firewall is disabled on the computer currently hooked up to the internet.

So why are these ports being blocked and how do I fix it?

[Dudlington]

Anyone? I think I fixed some of it by adding "Services" with the correct ports for each program in the advanced settings of the connection.

But with the firewall disabled, shouldn't I not have to do this?

Any ideas?