Darla,
I wasn't as computer knowlegeable then as I am now, plus more software has come out since that time. But, if I were managing a portrait artist today, I would put all the clients and prospects in a contact management program called Act! (the exclamation mark is part of their official title).
They were previously put out by Symantec, but must have been sold off because now it's put out by Interact Commerce Corporation. You can find information at
http://www.act.com
It's a wonderful program and very powerful. There's many things you can do with the information for each person once the data is entered. For example, you can create groups for mailings. For example, all the portrait agents in my files are in one group. Clients are another group I've defined and so on. You can also add custom fields. You can setup reminders for when to next contact a person. This is only a small sampling.
It's probably the most popular contact management program on the market.