cannot connect modem

i have and had big troubles setting up these com1/com2 etc plus the irq-settings when i tried to resinstall a modem. one pci-card was working when i had to reisntall windows 98se over the old one.
it is ams 5187 board with via mvp4-chip, integrated sound and video, ps2-key and mouse plus usb, plus one serial-port. in bios i have port 1 and 2. when i made changings i deleted all com1 etc in device-manager plus modem. then it was recognized again. i could dial up almost all up the time, but connaction failed. cable is ok.