firewall/port forwarding questions

Hi. I hope I'm in the right forum for this. Ok, so I have four PCs running off of a linksys WRT54G wireless router. Since we got the router, the firewall it comes with has been blocking a lot of programs that we were able to run previously (torrent download applications, P2P connections, etc). I found information on a bittorrent site that suggests port forwarding. Is that what I should do? if so, how, and do I need to do it on all 4 computers, or just the ones that need to use the blocked programs? also, I have a program called port magic that came with my PC that seems like it would do what I need except it wont run, for whatever reason. Will this program help, if I get it to run? are there other programs out there that will do the same thing? basically, I just want to be able to allow programs of my choice to access the internet without compromising the security of my home network.

thanks in advance. sorry if my rambling is confusing!

kristie

 

oh, I forgot to mention that our download and upload speeds are also terribly slow. I changed my MTU settings and that helped a little bit, but it's still slower than before we had this router.