Great I already have a great DS set up.
Now, I have my router set up with the firewall disabled, I placed my computer in the DMZ, and I forwarded all the necessary ports. I have even read a thorough walkthrough on how to set up a DS and how to forward ports. However my problem is recurring. I do have one theory that might work though. Have you tried connecting your PC directly to your cable modem? In other words, take the router out of the picture. It doesn't work for me - when I connect directly to the cable modem I lose my internet connection. I think this may be caused by me not using the right type of cable (I am using a straight-thru, not a crossover).
Anyhow, if you're even rustier at networking than I am, ignore the technicals and try plugging your computer directly into the cable modem via network cable and try these steps:
1. Check the internet to see if you're connected (brows more than just your home page)
2. Host a DS with a distinctive name
3. Turn on Halo, turn off all the filters and search by name
Good luck, although even if this does work, and I can get my computer surfing without a router, I would much prefer to continue working until I can get it running with a router (after all, other people in my house use the internet too).