I have a virgin broadband modam and a linksys

I have a virgin broadband modam and a linksys wrt54g wireless G Router, but i don't have the CD, I connected the router to the modem but could not get internet even though my computer said i am connected. I could or at least use to be able to connect to the routers web page http://192.168.1.1/ manage to make some configurations but I have left 3 security ports open 1.Block Anonymous Internet request
2 filter multicast 3. filter internet Nat Redirection. Is it dangerous to use the internets with these ports open?
I read some blogs relating to how one can get internet with the linksys wrt54g which said to take out the cable from the routers internet port and place it instead into one of the four routers ports this is what i have done. I then could get internet but have been unable to obtain wireless or routers web page, not even when I converted back the cables to their original positions i could no longer obtain routers web page. can u plz advise me thanks . And can you tell me do I have to have the CD inorder to have this router fully functioning? I was under the impression
one does'nt until i encountered these problems.