For Outlook Express:
You need the ISP's address for POP and SMTP. It will be something like pop.peoplepc.com. Both values will be different. You also need your username and password. Once you have those, it's simple to plug them in to Outlook Express.
Sound like it's completely buggered up. Can she boot into safe mode and get a full screen? I'm not sure though if you can run Norton in safe mode. Doesn't XP also have a feature that lets you roll back to a last known good configuration? If so, try that. There are also boot discs that will are loaded with software. Look on various sites for them. They will allow you to boot into your pc, do a virus scan, adware etc... then try booting XP again. The best thing to probably do is wipe out XP and reinstall it. If the PC is that old it's about time for a good cleansing anyways.