It turns out that a system migration to a new hard drive on a different drive controller resulted in the windows kernel booting from one location, but the boot file listed it on the old drive. So the update would install and link the kernel back to the old drive instead of where it should have been, and boom instantly unlinked boot sequence. This happened with any update that changed the kernel.

I attempted to do a complete reinstall from the original windows home cd, but it was so old it didn't have the required SATA support even with the required sata and raid drivers added in during installation. So I used a spare winXP pro license I has acquired for emergencies like this, and the re-install worked like a champ. Computer works fine, and I got almost everything I need/want/use from my backups and archives so it's actually a bit better now than it was.

The latest set of windows updates killed my computer. After the mandatory reboot, the computer locked up hard. It locks before the windows boot splash screen even shows, even when I boot using the various "F8" options. I used a ubuntu live cd to make sure it wasn't a hardware problem, and after mounting the windows partition I saw that trying the windows "logged" boot option wasn't even getting far enough to create the log file.

According to the windowsupdate.log file, the following updates were successfully installed:
KB929338
KB929399
KB890830
Root Certificates

The first one supposedly fixes a race condition and it replaces the nt kernel file, so it's possible it's not compatible with my hardware. Here is what I am running, and it was very stable until this update:

winXP home (fully patched and updated)
Athlon 64 X2 4400
2 gig ram
NForce3 based motherboard
AGP Nvidia 6800GT
Audigy 2 ZS soundcard
Onboard nvidia network interface