msn9 and dial up please help

I am having a problem with my parents brand new computer. They don't want to go to dsl or cable modem so I installed msn9 dial up. The problem I am having and can't seem to figure a solution to is, after initial install msn9 works fine, dials out, connects and functions, but if I shut the computer down and restart I can't get msn to connect to the internet. I get dial tone and the modem dials out however after about 15 seconds I get a message that says "Please try your call again." I tried changing dail up numbers, no help. I reinstall msn and it works until I shut the computer down and restart then same problem. It seems that something in the system is defaulting to original configuration but I don't know what. does anyone have any suggestions? I contacted msn customer service but they are useless.
BTW the computer has ASUS p4p800 board, 3.0 processor, 1 gig ram, 56k modem