internet connection troubles

I can be online from 5 -15 minutes and then can loose connection. I am on a dsl line. I can get disconnected in middle of download,timing out not a possible scenario. Will run ipconfig /release and /renew and then be ok for up to 15 minutes possibly. I have started over on a fresh install and format of HD to see if problem can be recreated and it can recreate itself. After dropped connection cannot ping anything but 127.0.0.1. Apparently ISP doesnt seem to have a clue. Any ideas Please????