I would guess you are at the minimum specs for a winmodem. Even a cheap hardware modem is going to perform better than this USR in a 166.

in either case I have never installed modem drivers first, some usb devices I have, but not modems.

So i still say clean up all old drivers installs, shut down install modem and when windows finds new device let it install the drivers

may even try new drivers from...

<a href="http://www.usr.com/support/s-main-menu.asp" target="_blank">http://www.usr.com/support/s-main-menu.asp</a>