Well, he needs to change the new computer's name to the same one his old computer had. Then he has to duplicate all the IP settings. Finally, if he's using a new NIC card, he needs to call @home and have them recognize it.
Better yet, if this is all Greek to him, just have him call @home's 888 number and let them talk him through it, and push the new NIC while they're at it.
Have them talk him through setting up his E-mail program too, or it wont work either. The setting and addresses are different for each city.