TegGhola , thank you so much for your confirmation of what I suspected. I was fairly sure that I couldn't have two DSL modems on the same phone line, but was not %100 sure. Although I plugged the Speedstream in and observed the DSL stop working, I wanted to make sure it wasn't some setting or some other thing that I was overlooking. I have a teen in the house that had a Linksys wireless gaming adaptor that apperently has gone bad, and he wanted to take a spare Speedstream and plug his game directly into that in his room. I don't think he believed me, so I wanted to confirm what I thought and you have done this.
My house was built by an electrician and he added a LOT of phone outlets and I think he used CAT V wiring (I am not strong with networking and cabling), so I need to look into putting the wireless modem in the basement and somehow changing some of the connections in the box downstairs to cause some of the phone outlets to become ethernet outlets. Of course, the quickest and easiest way to solve our problem is to replace the gaming adapter, but his finances precludes this from happening anytime soon.