I have just built a pc using an Intel mobo and cpu, and am running XP
Pro. XP and all devices are using the most recent patches / fixes.
The pc is running fantastically in all other respects, with no other
issues nor performance problems.

My old PC used an ISP-supplied network card, but my mobo has built-in
LAN, which I am using.

If I leave the Local Area Connection enabled when I shut down, booting
show the XP splash / starting screen, but I never get the user login /
select which user to login screen. Shortly after the splash screen
fades, the drive access light goes out, and the monitor goes into power
save mode.

Booting to safe mode *always* works, with and without network
connection. Network connection works in safe mode.

Boot to last-known good settings does not work.

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If I *disable* the LAN connection before shutdown, the boot always
works. Connecting the cable modem using USB also works.
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I have *not* set my ISP's IP address in the IP Properties
configuration, instead allowing "Obtain an IP address automatically.
(This is a suggested work-around.)

I have found very few search results for this problem, and wanted to
document it for others having the same problem.