David,
Have you installed the latest Sp1, or SP2 for windows Xp? Have you added any software recently to this system? Have you made any changes whatsoever?

Does this machine have an external PCI NIC? Or is the NIC on the motherboard?

Couple of suggestions:

One, click start, click run, and type:
sfc /scannow

Make sure you have the XP home disk ready. It will check your system files and make sure they are not corrupt. If it finds a corrupt file, it will replace it.

Another thing, are you using Zone Alarm? If so, uninstall it, reboot, and tell me if you are getting the same issue.

Lastly, click start, click run, and type
msconfig

On the screen that pops up, select diagnostic startup. If that fixes your problem, then something that is loading during startup is causing the boot hangs. Slowly add the items from the startup tab in msconfig, until you get the problem again.

Once you find the item that is hanging your system, post it up here, and we might be able to help you further.