Win 2000 Pro S P4 Win Modem

I am rinning Win 2000 Pro w/Service Pack 3, on a DELL Inspiron 7000 laptop. I had installed SP4; but, my modem(LT Win Modem) stopped working and would not connect to the Internet, and any search inquries frooze my browser for 1-2 min. except when I used Firefox. Since then, I have reverted to SP3. My modem works, but still have a problem with search boxes. Microsoft “Windows update,” insist I downoad this update before allowing others downloads from its site. I have tried everything I know even,contacting other sites icl. Microsoft with no results.
How do I resolve this SP4/Win modem problem?

Thanks in Advance,

Abd’al-Karim