Thanks. The machine came with XP SP1a and I have not yet installed SP2, as I want to get this thing relatively stable before I add another level of uncertainty.

I had already run sfc /scannow and found no problems. I am not running ZoneAlarm, though I am running PC-Cillin with firewall enabled. The boot hang is erratic -- sometimes it boots, sometimes not, so the disable-items-in-msconfig thing isn't really helpful, as it does not reliably hang. What is reliable is that when it hangs, it hangs trying to load AFD.SYS, as noted in my original post. That seems to be the problem item. It may be that AFD.SYS is interacting poorly with some other item, but if so it happens only at boot time, and not at every boot. Perhaps if I knew more about what AFD.SYS does, it would help me to eliminate a problem. From your ZoneAlarm question, I'm wondering if the PC-CILLIN firewall could be an issue; what's your reasoning?

Thanks,
David