Win XP and IBM Thinkpad Int. modem issue

I currently run Win XP on an IBM 600E Thinkpad with a Thinkpad Int Modem. The modem registers an “internal modem error” after its first usage and Xp is restarted. According to the Microsoft website the Current Driver for XP does not support the Wakeon ring (WOR) feature and I neeed to upgrade from the XP site. However when I try to download relevant drivers from the Microsoft or Ibm sites, I only get driver files up to Windows 2000. Nothing exists for Xp.
Can you assist in finding related XPupgrades that can solve this or any other problems?