Set yourself up as administrator and use a password to get in. Anyone else, set them up as a secondary user without administrative privileges. They need a password also. There is a guest setting in XP that has limited use. This is good because it also means that viruses or mal-ware can't write to the registry if a non-administrator is using the machine. So this means you should have a second setup for yourself and only go in as administrator when you need to.

SRS