Mac & pc on same router

I had a PC hooked up to a cable modem through my local cable service provider. I also have digital cable and phone. I recently bought a rebuilt Mac O SX version 10. I used a modem I already had to connect the Mac but I was not able to connect to the...

internet. I called the cable company and the first csr told me it was impossible to use 2 modems and I must get a wireless router. So I got the cable co. to come out and install the wireless modem but the cable guy said I had to contact mac support to give them a web key and another code or # in order to have the mac run off the wireless router. Some one else is telling me I need an airport?! I cant seem to find the right number for Mac support and the Cable support people are useless. Any ideas?
1 hour ago - 3 days left to answer.

First do you know if your mac has wireless? If its a desktop mac more that likely it doesn't, but if its a macbook then it should. What the cable company should have recommended was a router or a switch and not a wireless modem. What you should do is return the wireless modem and get a normal modem and go but a router. A router will allow you to hook up more than one computer to your cable modem.

If you need anything else please let me know.