Just now, I went to dial up to the internet on my other computer, and it would go through everything to verifying username and password and then disconnect saying that it was unable to make a connection. It gave me a "error:720" message. I know that it is not my phone line or ISP because I can get on the internet with my other computer. Has anyone else had an similar experience. I am thinking that my modem took a dump, but I would like to know for sure before I buy another one. I am not familair with the 720 error message. Thank You.

This may help http://support.microsoft.com/default.aspx?scid=kb;EN-US;q312840 .

This link also shows some solutions for 720 error message and some more links to microsoft website. Error 720 solutions (http://www.eicon.com/support/helpweb/diva/dunmsg.asp?n=720)

It seems more likely to me that you have a problem with your DUN module in windows, why not swap out your modem with another and test the new one on your problem machine (that way you can tell if its software or hardware) before buying anything.