This looks like the same error I posted about a couple of months ago under "svchost.exe crashes each time". My system is a Windows 2000 SP4 machine as well, but with a different modem and modem drivers.
It runs Norton Antivirus 2004, which may be a suspect. Does your problem machine run NAV 2004 as well?
I still have not found a solution though, temporarily disabling NAV2004 makes no difference.
The problem is not a "blue screen of death" like nchcraig mentions.