Adding a mac to network places

In media center, I've run the network setup utility on all 3 of my computers,
well,all except the mac as I can't find a setup utility to add any other
computers. My Gateway laptop can network with my roommates Compaq (real old
one, celeron processor).

Sometimes in using the wireless network, I have to unplug the router to just
get the 2 windows pcs back on the network. I've gotten the latest firmware
for the router which was supposed to fix this, but it didn't. I still have
to unplug and then the mac won't go on, I have to try to run an ethernet
cable, but this is inconvenient, I don't have in the wall plug in the
computer room so people trip over the cabling.

Anyone experience this with a Linksys G router and a mac on their network?

Harry