Okay, I think I can rule ZoneAlarm out as the problem. I uninstalled it completely, and then reinstalled a later version (4.5). It crashed about an hour later. Since ZA has been on this computer for around three years now, and the new install still crashes, it seems unlikely to be the source. I am going to try to uninstall the last Windows Update. Thanks for your help.
Here is the latest debug session (in the hope that someone spots something it that is meaningful.)
Loading Dump File [C:\WINNT\MEMORY.DMP]
Kernel Complete Dump File: Full address space is available
Symbol search path is: srv*c:\symbols*
http://msdl.microsoft.com/download/symbols
Executable search path is: C:\WINNT
Loading symbols for 80400000 ntoskrnl.exe -> ntoskrnl.exe
ModLoad: 80400000 8059cd80 ntoskrnl.exe
Windows 2000 Kernel Version 2195 (Service Pack 4) UP Free x86 compatible
Product: WinNt
Kernel base = 0x80400000 PsLoadedModuleList = 0x80481580
Debug session time: Sat Mar 25 16:42:44.042 2006 (GMT-7)
System Uptime: 0 days 0:36:11.722
Loading symbols for 80400000 ntoskrnl.exe -> ntoskrnl.exe
ModLoad: 80400000 8059cd80 ntoskrnl.exe
Loading Kernel Symbols
.ModLoad: 80062000 80072520 halacpi.dll
.ModLoad: f7410000 f7412a20 \WINNT\System32\BOOTVID.dll
.ModLoad: bffd8000 bffffc20 ACPI.sys
.ModLoad: f75c8000 f75c8f80 \WINNT\System32\DRIVERS\WMILIB.SYS
.ModLoad: f7000000 f700e6a0 pci.sys
.ModLoad: f7010000 f701b680 isapnp.sys
.ModLoad: f7414000 f7416320 compbatt.sys
.ModLoad: f7500000 f7501b00 \WINNT\System32\DRIVERS\BATTC.SYS
.ModLoad: f7502000 f7503100 intelide.sys
.ModLoad: f7280000 f7285520 \WINNT\System32\DRIVERS\PCIIDEX.SYS
.ModLoad: bffbd000 bffd7b00 pcmcia.sys
.ModLoad: bffa0000 bffbc220 ftdisk.sys
.ModLoad: f7504000 f7505d20 Diskperf.sys
.ModLoad: bff7e000 bff9f9c0 dmio.sys
.ModLoad: f7418000 f741ac00 ACPIEC.sys
.ModLoad: f741c000 f741ed00 PartMgr.sys
.ModLoad: f7288000 f728f4c0 MountMgr.sys
.ModLoad: bff68000 bff7d180 atapi.sys
.ModLoad: f7290000 f7297720 disk.sys
.ModLoad: f7020000 f7028700 \WINNT\System32\DRIVERS\CLASSPNP.SYS
.ModLoad: bff56000 bff677c0 KSecDD.sys
.ModLoad: bfed3000 bff555a0 Ntfs.sys
.ModLoad: bfea9000 bfed2aa0 NDIS.sys
.ModLoad: bfe93000 bfea8be0 Mup.sys
.ModLoad: f7298000 f729d100 agp440.sys
.ModLoad: f747c000 f747e5a0 \SystemRoot\System32\DRIVERS\CmBatt.sys
.ModLoad: f7040000 f704c4c0 \SystemRoot\System32\DRIVERS\VIDEOPRT.SYS
.ModLoad: bfe50000 bfe616c0 \SystemRoot\System32\DRIVERS\atimpab.sys
Unable to read image header at f72b8000
.ModLoad: f72b8000 f72bf000 \SystemRoot\System32\DRIVERS\fdc.sys
.ModLoad: f72c8000 f72ce100 \SystemRoot\System32\DRIVERS\parport.sys
.ModLoad: f7050000 f705f400 \SystemRoot\System32\DRIVERS\serial.sys
.ModLoad: f7484000 f7487640 \SystemRoot\System32\DRIVERS\serenum.sys
.ModLoad: f7060000 f7068c00 \SystemRoot\System32\DRIVERS\smcirda.sys
.ModLoad: f748c000 f748e720 \SystemRoot\System32\DRIVERS\irenum.sys
.ModLoad: f7070000 f707b680 \SystemRoot\System32\DRIVERS\i8042prt.sys
.ModLoad: f72e0000 f72e5ec0 \SystemRoot\System32\DRIVERS\kbdclass.sys
.ModLoad: f72f0000 f72f4fc0 \SystemRoot\system32\DRIVERS\USBD.SYS
.ModLoad: bfde5000 bfe27020 \SystemRoot\system32\DRIVERS\SynTP.sys
.ModLoad: f7300000 f7305400 \SystemRoot\System32\DRIVERS\mouclass.sys
.ModLoad: f7080000 f708e180 \SystemRoot\System32\Drivers\Cdr4_2K.SYS
.ModLoad: f7318000 f731ec40 \SystemRoot\System32\DRIVERS\cdrom.sys
.ModLoad: f7328000 f732d560 \SystemRoot\System32\Drivers\Cdralw2k.SYS
.ModLoad: f7330000 f7337f40 \SystemRoot\System32\DRIVERS\uhcd.sys
.ModLoad: bfd78000 bfd97d00 \SystemRoot\system32\drivers\KS.SYS
.ModLoad: bfd98000 bfdbc1e0 \SystemRoot\system32\drivers\portcls.sys
.ModLoad: bfdbd000 bfde4c40 \SystemRoot\system32\drivers\maestro.sys
.ModLoad: bfd13000 bfd77f00 \SystemRoot\System32\DRIVERS\ltmdmnt.sys
.ModLoad: f7368000 f736f0e0 \SystemRoot\System32\Drivers\Modem.SYS
.ModLoad: f75f0000 f75f0a40 \SystemRoot\System32\DRIVERS\audstub.sys
.ModLoad: f74ac000 f74afe60 \SystemRoot\System32\DRIVERS\TDI.SYS
.ModLoad: f7378000 f737ccc0 \SystemRoot\System32\DRIVERS\rasirda.sys
.ModLoad: f7090000 f709ca80 \SystemRoot\System32\DRIVERS\rasl2tp.sys
.ModLoad: f74b4000 f74b62e0 \SystemRoot\System32\DRIVERS\ndistapi.sys
.ModLoad: bfcfc000 bfd12ba0 \SystemRoot\System32\DRIVERS\ndiswan.sys
.ModLoad: f70a0000 f70abc40 \SystemRoot\System32\DRIVERS\raspptp.sys
.ModLoad: f7398000 f739c400 \SystemRoot\System32\DRIVERS\ptilink.sys
.ModLoad: f73a8000 f73ac0e0 \SystemRoot\System32\DRIVERS\raspti.sys
.ModLoad: f70b0000 f70bea20 \SystemRoot\System32\DRIVERS\parallel.sys
.ModLoad: f75fb000 f75fc000 \SystemRoot\System32\DRIVERS\swenum.sys
.ModLoad: bfcd1000 bfcfb3a0 \SystemRoot\System32\DRIVERS\update.sys
.ModLoad: bfcbd000 bfcd05e0 \SystemRoot\system32\DRIVERS\WscNetDr.sys
Unable to read image header at f73c0000
.ModLoad: f73c0000 f73c5000 \SystemRoot\System32\DRIVERS\flpydisk.sys
.ModLoad: f70f0000 f70f9be0 \SystemRoot\System32\DRIVERS\usbhub.sys
.ModLoad: f7100000 f7109ce0 \SystemRoot\System32\Drivers\NDProxy.SYS
.ModLoad: f73d0000 f73d6a20 \SystemRoot\System32\Drivers\EFS.SYS
.ModLoad: f73e8000 f73ed320 \SystemRoot\System32\DRIVERS\USBSTOR.SYS
.ModLoad: f74e4000 f74e7020 \SystemRoot\System32\DRIVERS\usbscan.sys
Unable to read image header at f7510000
.ModLoad: f7510000 f7512000 \SystemRoot\System32\Drivers\Fs_Rec.SYS
Unable to read image header at f760a000
.ModLoad: f760a000 f760b000 \SystemRoot\System32\Drivers\Null.SYS
.ModLoad: f760c000 f760cee0 \SystemRoot\System32\Drivers\Beep.SYS
.ModLoad: f74f4000 f74f7580 \SystemRoot\System32\drivers\vga.sys
.ModLoad: f760f000 f760ff80 \SystemRoot\System32\Drivers\mnmdd.SYS
.ModLoad: f7408000 f740d240 \SystemRoot\System32\Drivers\Msfs.SYS
.ModLoad: f7110000 f7118fa0 \SystemRoot\System32\Drivers\Npfs.SYS
.ModLoad: f7518000 f7519e40 \SystemRoot\System32\DRIVERS\rasacd.sys
.ModLoad: bfc06000 bfc541a0 \SystemRoot\System32\DRIVERS\tcpip.sys
.ModLoad: f7120000 f7128680 \SystemRoot\System32\DRIVERS\msgpc.sys
.ModLoad: f72d0000 f72d7d00 \SystemRoot\System32\DRIVERS\wanarp.sys
.ModLoad: bfbde000 bfc05e00 \SystemRoot\System32\DRIVERS\netbt.sys
.ModLoad: f7130000 f71381a0 \SystemRoot\System32\DRIVERS\netbios.sys
.ModLoad: bfb14000 bfb3d900 \SystemRoot\System32\DRIVERS\rdbss.sys
.ModLoad: bfa9d000 bfb01ca0 \SystemRoot\System32\DRIVERS\mrxsmb.sys
.ModLoad: bf9e2000 bfa9c6e0 \SystemRoot\System32\Drivers\avg7core.sys
.ModLoad: f751e000 f751f0c0 \SystemRoot\System32\Drivers\avg7rsw.sys
.ModLoad: f7308000 f730e8e0 \SystemRoot\System32\Drivers\avg7rsnt.sys
.ModLoad: bf9bf000 bf9e13c0 \SystemRoot\System32\Drivers\Fastfat.SYS
.ModLoad: f7160000 f716efe0 \SystemRoot\System32\Drivers\Cdfs.SYS
.ModLoad: f7640000 f7640f80 \SystemRoot\System32\Drivers\dump_WMILIB.SYS
.ModLoad: bf981000 bf996180 \SystemRoot\System32\Drivers\dump_atapi.sys
.ModLoad: a0000000 a0190000 \??\C:\WINNT\system32\win32k.sys
Unable to read image header at bf960000
.ModLoad: bf960000 bf981000 \SystemRoot\System32\atidrab.dll
.ModLoad: f7674000 f7674ba0 \SystemRoot\System32\Drivers\V7.SYS
.ModLoad: bfb9e000 bfbabec0 \SystemRoot\System32\DRIVERS\irda.sys
.ModLoad: bf144000 bf147760 \SystemRoot\system32\DRIVERS\mdc8021x.sys
.ModLoad: bf007000 bf01fe00 \SystemRoot\System32\DRIVERS\nbf.sys
.ModLoad: beff0000 bf006400 \SystemRoot\System32\DRIVERS\nwlnkipx.sys
.ModLoad: bfb8e000 bfb9dee0 \SystemRoot\System32\DRIVERS\nwlnknb.sys
.ModLoad: befd2000 befef4a0 \SystemRoot\System32\drivers\afd.sys
Unable to read NT module Full Name string at e31f8fa8 - NTSTATUS 0xC0000147
.ModLoad: f7170000 f717e360 nwlnkspx.sys
.ModLoad: f7360000 f7365900 \SystemRoot\System32\DRIVERS\HIDPARSE.SYS
.ModLoad: f7348000 f734dfa0 \SystemRoot\System32\DRIVERS\HIDCLASS.SYS
Unable to read image header at f757a000
.ModLoad: f757a000 f757c000 \SystemRoot\System32\Drivers\ParVdm.SYS
.ModLoad: beed0000 beee1f80 \SystemRoot\system32\drivers\wdmaud.sys
.ModLoad: bf070000 bf07b8c0 \SystemRoot\system32\drivers\sysaudio.sys
.ModLoad: f7586000 f7587380 \??\C:\WINNT\System32\Drivers\avgtdi.sys
.ModLoad: f71d0000 f71d8240 \SystemRoot\System32\Drivers\Fips.SYS
.ModLoad: bed58000 bed92440 \SystemRoot\System32\DRIVERS\srv.sys
.ModLoad: beca8000 becb7a20 \SystemRoot\System32\DRIVERS\ipsec.sys
.ModLoad: f74a4000 f74a7d80 \??\C:\PROGRA~1\Belkin\BELKIN~1.11G\DNINDIS5.SYS
.ModLoad: be89e000 be8a0dc0 \SystemRoot\System32\DRIVERS\ndisuio.sys
.ModLoad: be61e000 be654720 \??\C:\WINNT\System32\vsdatant.sys
.ModLoad: be522000 be555880 \SystemRoot\system32\DRIVERS\RT2500.sys