my modem sucks

I am currently using a modem blaster di5630-5 pci 56k modem in my pc and am getting unwanted disconnects at all times dring online use. My brother recently had the modem in his pc and it did the same thing to him until he added an init string to it but every init string i try on it still fails. Other specs for pc are AMD semperon 3000+ processor 512 meg pc3200 ram built for gaming