just covering the bases... but do you have a Cable / DSL router?
something like this:
http://www.newegg.com/Product/Product.asp?Item=N82E16833156001
I was able to split my cable internet up to 3 computers in under 20min once I plugged my cable modem into a similar router & follwed the directions that came w/ the router.
-another way to do it-
a couple years ago I had WIFI at my apartment, I bought a USB wireless network card & plugged that into my computer, then set up my computer to "share the internet" from my network card to the local router
as long as that computer was on & the crappy WIFI was working (/bout 75% of the time), I had up to 4 more computers online through a normal router
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good luck setting things up. Two biggest things to remember are: 1-Restarting solves 90% of all problems. & 2-When problem searching / solving, use a process of elmination to find where the issue is.
(Check cables. Check modem is connecting to network. Check to see if 1 computer can get online. baby step etc. etc. etc.)